Sarbati asked   •  13 minutes ago

Read the following passage and answer the questions that follows:
Nearly a century ago, biologists found that if they separated an invertebrate animal embryo into two parts at an early stage of its life, it would survive and develop as two normal embryos. This led them to believe that the cells in the early embryo are undetermined in the sense that each cell has the potential to develop in a variety of different ways. Later biologists found that the situation was not so simple. It matters in which plane the embryo is cut. If it is cut in a plane different from the one used by the early investigators, it will not form two whole embryos.
A debate arose over what exactly was happening. Which embryo cells are determined, just when do they become irreversibly committed to their fates, and what are the “morphogenetic determinants” that tell a cell what to become? But the debate could not be resolved because no one was able to ask the crucial questions in a form in which they could be pursued productively. Recent discoveries in molecular biology, however, have opened up prospects for a resolution of the debate. Now investigators think they know at least some of the molecules that act as morphogenetic determinants in early development. They have been able to show that, in a sense, cell determination begins even before an egg is fertilized.
Studying sea urchins, biologist Paul Gross found that an unfertilized egg contains substances that function as morphogenetic determinants. They are located in the cytoplasm of the egg cell; i.e., in that part of the cell’s protoplasm that lies outside of the nucleus. In the unfertilized egg, the substances are inactive and are not distributed homogeneously. When the egg is fertilized, the substances become active and, presumably, govern the behavior of the genes they interact with. Since the substances are unevenly distributed in the egg, when the fertilized egg divides, the resulting cells are different from the start and so can be qualitatively different in their own gene activity.
The substances that Gross studied are maternal messenger RNA’s –products of certain of the maternal genes. He and other biologists studying a wide variety of organisms have found that these particular RNA’s direct, in large part, the synthesis of histones, a class of proteins that bind to DNA. Once synthesized, the histones move into the cell nucleus, where sections of DNA wrap around them to form a structure that resembles beads, or knots, on a string. The beads are DNA segments wrapped around the histones; the string is the intervening DNA. And it is the structure of these beaded DNA strings that guides the fate of the cells in which they are located.
Q. According to the passage, the morphogenetic determinants present in the unfertilized egg cell are which of the following?
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How many factors of 24 × 35 × 104 are perfect squares which are greater than 1?
[2019]
  • a)
    42
  • b)
    43
  • c)
    44
  • d)
    45
Correct answer is option 'C'. Can you explain this answer?

Som Singh answered  •  1 hour ago
24 × 35 × 104 = 28 × 35 × 54
For perfect squares, we have to take only even powers of the prime factors of the number
The number of ways 2’s can be used is 5 i.e. 20, 22, 24, 26, 28
The number of ways 3’s can be used is 3 i.e. 30, 32, 34
The number of ways 5’s can be used is 3 i.e. 50, 52, 54
Therefore, the total number of factors which are perfect squares = 5 × 3 × 3 = 45
But this also includes the number 1.
Hence excluding 1, the required number is 45 – 1 = 44.

If the sum of the following series is n/m (where m and n are co-prime). Find the value of m - n. 
  • a)
    941
  • b)
    761
  • c)
    841
  • d)
    821
Correct answer is option 'D'. Can you explain this answer?

Sh Ashok Kumar Prasad answered  •  1 hour ago
Let Nth term = 1 / ( 1+ n2 + n4)
= ½ [ 1 / (  n2 - n + 1) - 1 / ( 1+ n2 + n) ]
= Put n = 1, 2, 3, ……40
= ½[ 1 -  1 / 1641]  = 820 / 1641
Therefore m – n = 1641 – 820 = 821.

Read the passage given below and answer the questions that follow.
“When you’re dead, you’re dead,” I’d always told myself. “You’re childless, so what difference does it make who gets the money, if there’s any left, or the sentimental treasures?” By which I mean my mother’s “sterling” silver, which turned out to be plate, and my flea market discoveries.
But my 10-year-old standard poodle was another story. Unmentioned in the existing document, Henry would be left alone after I died: unfed, unwalked, unloved. Would he die, too, only to be discovered by a neighbor when he started to stink up the joint? I owed him better.
My elder care lawyer raised a skeptical eyebrow when I explained that the inspiration to update everything was my dog. I might as well review all the paperwork, I told him: the power of attorney, the health care proxy, the living will, a codicil here and there, the list of friends’ children who had always been my beneficiaries. But a full year went by while I looked guiltily at the file folder on my desk marked “new will.” That took me by surprise, as I’m not a procrastinator. Remember the hated kid in high school who always had her papers done way in advance and went to the movies while everyone else was pulling an all-nighter? That was me.
But my lawyer, Gregg M. Weiss, was used to people starting the process and then disappearing. “That’s the No. 1 bane of my existence,” he said when I finally resurfaced, all papers ready to be signed.
“Whatever is on anyone’s to-do pile, this typically goes to the bottom. It’s avoidance, not facing the reality of death. The 80-year- olds we see are different. They don’t dillydally.” My mother had needed no admonitions about such things and had her affairs in order before she was out of her 50s, most likely because my father’s sudden death had left her with a mess to clean up when one least needs to be cleaning up messes. My new will splits the difference between being smart and being stubborn. Friends’ children remain the main beneficiaries, along with charities. My health care proxy remains a sensible, loving and brave friend who says that she has no problem pulling the plug under the right circumstances. Another friend replaces the former No. 2 for reasons of geography: A health care proxy who lives 3,000 miles away is not very likely to be available when you need her. My brother is grateful, as he always has been, to be spared that task. He wants me to have the kind of death I choose, but not to be in charge of it. Custody of Henry, my dog, goes to his walker, who loves him so much (and vice versa) that she has refused money to cover his care.
 
Q. Why did the author give Henry’s custody to his brother’s walker?
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Amrik Singh answered  •  1 hour ago
The passage mentions “Custody of Henry, my dog, goes to his walker, who loves him so much (and vice versa) that she has refused money to cover his care.” Option 1 cannot be corroborated from the passage. Considering the author is wealthy, the walker not charging a fee would not be a motivating factor to give her dog to her. Option 3 cannot be corroborated from the passage. The walker loved Henry, and more importantly Henry loved the walker. This would have convinced the author to give custody of Henry to the walker.
Hence, the correct answer is option 4.

DIRECTIONS for the question:
Solve the following question and mark the best possible option.
A chain smoker buys two matchboxes filled with n matchsticks each. Every time he needs a matchstick, he chooses one of the boxes at random and takes out a matchstick. One day, he takes out a matchbox and finds it empty. The probability that the other matchbox contains k (0 < k < n) matchsticks is
  • a)
  • b)
  • c)
  • d)
Correct answer is option 'B'. Can you explain this answer?

Kuldeep Singh answered  •  1 hour ago
The total number of matches is 2n. Since one of the  boxes is empty and the other has k matches, it means that 2n - k matches have already been used. The total number of ways of choosing any of these matches is 22n - k. Since we are interested in the empty box, we need to choose all n matches from that box.
This can be done in 2n - kCn ways. Thus the required probability is 

Om Prakash Beniwal asked   •  1 hour ago

Read the following passage and answer the questions that follows:
Nearly a century ago, biologists found that if they separated an invertebrate animal embryo into two parts at an early stage of its life, it would survive and develop as two normal embryos. This led them to believe that the cells in the early embryo are undetermined in the sense that each cell has the potential to develop in a variety of different ways. Later biologists found that the situation was not so simple. It matters in which plane the embryo is cut. If it is cut in a plane different from the one used by the early investigators, it will not form two whole embryos.
A debate arose over what exactly was happening. Which embryo cells are determined, just when do they become irreversibly committed to their fates, and what are the “morphogenetic determinants” that tell a cell what to become? But the debate could not be resolved because no one was able to ask the crucial questions in a form in which they could be pursued productively. Recent discoveries in molecular biology, however, have opened up prospects for a resolution of the debate. Now investigators think they know at least some of the molecules that act as morphogenetic determinants in early development. They have been able to show that, in a sense, cell determination begins even before an egg is fertilized.
Studying sea urchins, biologist Paul Gross found that an unfertilized egg contains substances that function as morphogenetic determinants. They are located in the cytoplasm of the egg cell; i.e., in that part of the cell’s protoplasm that lies outside of the nucleus. In the unfertilized egg, the substances are inactive and are not distributed homogeneously. When the egg is fertilized, the substances become active and, presumably, govern the behavior of the genes they interact with. Since the substances are unevenly distributed in the egg, when the fertilized egg divides, the resulting cells are different from the start and so can be qualitatively different in their own gene activity.
The substances that Gross studied are maternal messenger RNA’s –products of certain of the maternal genes. He and other biologists studying a wide variety of organisms have found that these particular RNA’s direct, in large part, the synthesis of histones, a class of proteins that bind to DNA. Once synthesized, the histones move into the cell nucleus, where sections of DNA wrap around them to form a structure that resembles beads, or knots, on a string. The beads are DNA segments wrapped around the histones; the string is the intervening DNA. And it is the structure of these beaded DNA strings that guides the fate of the cells in which they are located.
Q. It can be inferred from the passage that the initial production of histones after an egg is fertilized takes place
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Kalawati Devi asked   •  1 hour ago

Read the following passage and answer the questions that follows:
The majority of successful senior managers do not closely follow the classical rational model of first clarifying goals, assessing the problem, formulating options, estimating likelihoods of success, making a decision, and only then taking action to implement the decision. Rather, in their day-by-day tactical manoeuvres, these senior executives rely on what is vaguely termed “intuition” to manage a network of interrelated problems that require them to deal with ambiguity, inconsistency, novelty, and surprise; and to integrate action into the process to thinking.
Generations of writers on management have recognized that some practicing managers rely heavily on intuition. In general, however, such writers display a poor grasp of what intuition is. Some see it as the opposite of rationality; others view it as an excuse for capriciousness.
Isenberg’s recent research on the cognitive processes of senior managers reveals that managers’ intuition is neither of these. Rather, senior managers use intuition in at least five distinct ways. First, they intuitively sense when a problem exists. Second, managers rely on intuition to perform well-learned behaviour patterns rapidly. This intuition is not arbitrary or irrational, but is based on years of painstaking practice and hands-on experience that build skills. A third function of intuition is to synthesize isolated bits of data and practice into an integrated picture, often in an “Aha!” experience. Fourth, some managers use intuition as a check on the results of more rational analysis. Most senior executives are familiar with the formal decision analysis models and tools, and those who use such systematic methods for reaching decisions are occasionally leery of solutions suggested by these methods which run counter to their sense of the correct course of action. Finally, managers can use intuition to bypass in-depth analysis and move rapidly to engender a plausible solution. Used in this way, intuition is an almost instantaneous cognitive process in which a manager recognizes familiar patterns.
One of the implications of the intuitive style of executive management is that “thinking” is inseparable from acting. Since managers often “know” what is right before they can analyze and explain it, they frequently act first and explain later. Analysis is inextricably tied to action in thinking/acting cycles, in which managers develop thoughts about their companies and organizations not by analyzing a problematic situation and then acting, but by acting and analyzing in close concert.
Given the great uncertainty of many of the management issues that they face, senior managers often instigate a course of action simply to learn more about an issue. They then use the results of the action to develop a more complete understanding of the issue. One implication of thinking/acting cycles is that action is often part of defining the problem, not just of implementing the solution.
Q. It can be inferred from the passage that which of the following would most probably be one major difference in behaviour between Manager X, who uses intuition to reach decisions, and Manager Y, who uses only formal decision analysis?
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Kamla Devi asked   •  1 hour ago

Read the following passage and answer the questions that follows:
Archaeology as a profession faces two major problems. First, it is the poorest of the poor. Only paltry sums are available for excavating and even less is available for publishing the results and preserving the sites once excavated. Yet archaeologists deal with priceless objects every day.
Second, there is the problem of illegal excavation, resulting in museum-quality pieces being sold to the highest bidder.
I would like to make an outrageous suggestion that would at one stroke provide funds for archaeology and reduce the amount of illegal digging. I would propose that scientific archeological expeditions and governmental authorities sell excavated artifacts on the open market. Such sales would provide substantial funds for the excavation and preservation of archaeological sites and the publication of results. At the same time, they would break the illegal excavator’s grip on the market, thereby decreasing the inducement to engage in illegal activities.
You might object that professionals excavate to acquire knowledge, not money. Moreover, ancient artifacts are part of our global cultural heritage, which should be available for all to appreciate, not sold to the highest bidder. I agree. Sell nothing that has unique artistic merit or scientific value. But, you might reply, everything that comes out of the ground has scientific value. Here we part company. Theoretically, you may be correct in claiming that every artifact has potential scientific value. Practically, you are wrong.
I refer to the thousands of pottery vessels and ancient lamps that are essentially duplicates of one another. In one small excavation in Cyprus, archaeologists recently uncovered 2,000 virtually indistinguishable small jugs in a single courtyard, even precious royal seal impressions known as melekh handles have been found in abundance — more than 4,000 examples so far.
The basement of museums is simply not large enough to store the artifacts that are likely to be discovered in the future. There is not enough money even to catalogue the finds; as a result, they cannot be found again and become as inaccessible as if they had never been discovered. Indeed, with the help of a computer, sold artifacts could be more accessible than are the pieces stored in bulging museum basements. Prior to sale, each could be photographed and the list of the purchasers could be maintained on the computer A purchaser could even be required to agree to return the piece if it should become needed for scientific purposes. It would be unrealistic to suggest that illegal digging would stop if artifacts were sold in the open market. But the demand for the clandestine product would be substantially reduced. Who would want an unmarked pot when another was available whose provenance was known, and that was dated stratigraphically by the professional archaeologist who excavated it?
Q. The author implies that all of the following statements about duplicate artifacts are true EXCEPT:
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Omee Devi asked   •  1 hour ago

Read the following passage and answer the questions that follows:
Federal efforts to aid minority businesses began in the 1960’s when the Small Business Administration (SBA) began making federally guaranteed loans and governmentsponsored management and technical assistance available to minority business enterprises. While this program enabled many minority entrepreneurs to form new businesses, the results were disappointing, since managerial inexperience, unfavorable locations, and capital shortages led to high failure rates. Even 15 years after the program was implemented, minority business receipts were not quite two percent of the national economy’s total receipts. Recently federal policymakers have adopted an approach intended to accelerate development of the minority business sector by moving away from directly aiding small minority enterprises and toward supporting larger, growth-oriented minority firms through intermediary companies. In this approach, large corporations participate in the development of successful and stable minority businesses by making use of government-sponsored venture capital. The capital is used by a participating company to establish a Minority Enterprise Small Business Investment Company or MESBIC. The MESBIC then provides capital and guidance to minority businesses that have potential to become future suppliers or customers of the sponsoring company.
MESBIC’s are the result of the belief that providing established firms with easier access to relevant management techniques and more job-specific experience, as well as substantial amounts of capital, gives those firms a greater opportunity to develop sound business foundations than does simply making general management experience and small amounts of capital available. Further, since potential markets for the minority businesses already exist through the sponsoring companies, the minority businesses face considerably less risk in terms of location and market fluctuation. Following early financial and operating problems, sponsoring corporations began to capitalize MESBIC’s far above the legal minimum of $500,000 in order to generate sufficient income and to sustain the quality of management needed. MESBIC’s are now emerging as increasingly important financing sources for minority enterprises.
Ironically, MESBIC staffs, which usually consist of Hispanic and Black professionals, tend to approach investments in minority firms more pragmatically than do many MESBIC directors, who are usually senior managers from sponsoring corporations. The latter often still think mainly in terms of the “social responsibility approach” and thus seem to prefer deals that are riskier and less attractive than normal investment criteria would warrant. Such differences in viewpoint have produced uneasiness among many minority staff members, who feel that minority entrepreneurs and businesses should be judged by established business considerations. These staff members believe their point of view is closer to the original philosophy of MESBIC’s and they are concerned that, unless a more prudent course is followed, MESBIC directors may revert to policies likely to re-create the disappointing results of the original SBA approach.
Q. Which of the following does the author cite to support the conclusion that the results of the SBA program were disappointing?
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Samsher Singh asked   •  1 hour ago

Refer to the data below and answer the questions that follow.
Two metal traders - Rahul and Anil - trade in metals P and Q only. The chart given below displays the performance (price in Rs. per 10 gm) of the two metals on five days of a particular week.
Rahul: He sold metal P on Monday and Tuesday in the ratio 1:2 by weight. On Wednesday and Friday each, he bought back half of the entire quantity of metal P sold earlier.
He bought metal Q on Tuesday and sold it in equal quantity on Thursday.
Anil: He sold metal P on Monday and Tuesday such that the amounts received on Monday and Tuesday are in the ratio 25 : 28. On Wednesday, he bought back the entire quantity of metal P sold on the previous two days. He bought metal Q on the first three days of the week in equal quantities, and on Thursday, sold 50% of the quantity of metal Q bought over the first three days of the week. On Friday, he sold the remaining 50% of the quantity of metal Q purchased over the first three days of the week.
The profit/loss made by a trader during a particular week is the difference between the amount that he obtains by selling metal and the amount that he spends in buying metal. "Margin" for a week is the profit/loss expressed as a percentage of the total amount obtained by selling metal during that week. The net profit/loss made by Rahul on transactions made for metal P and Q are the same. This holds true for Anil as well. The total net loss on the transactions made by Rahul and Anil is the same.
Q. What is the approximate loss margin for Anil?
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Umed Singh asked   •  1 hour ago

Read the following passage and answer the questions that follows:
Nearly a century ago, biologists found that if they separated an invertebrate animal embryo into two parts at an early stage of its life, it would survive and develop as two normal embryos. This led them to believe that the cells in the early embryo are undetermined in the sense that each cell has the potential to develop in a variety of different ways. Later biologists found that the situation was not so simple. It matters in which plane the embryo is cut. If it is cut in a plane different from the one used by the early investigators, it will not form two whole embryos.
A debate arose over what exactly was happening. Which embryo cells are determined, just when do they become irreversibly committed to their fates, and what are the “morphogenetic determinants” that tell a cell what to become? But the debate could not be resolved because no one was able to ask the crucial questions in a form in which they could be pursued productively. Recent discoveries in molecular biology, however, have opened up prospects for a resolution of the debate. Now investigators think they know at least some of the molecules that act as morphogenetic determinants in early development. They have been able to show that, in a sense, cell determination begins even before an egg is fertilized.
Studying sea urchins, biologist Paul Gross found that an unfertilized egg contains substances that function as morphogenetic determinants. They are located in the cytoplasm of the egg cell; i.e., in that part of the cell’s protoplasm that lies outside of the nucleus. In the unfertilized egg, the substances are inactive and are not distributed homogeneously. When the egg is fertilized, the substances become active and, presumably, govern the behavior of the genes they interact with. Since the substances are unevenly distributed in the egg, when the fertilized egg divides, the resulting cells are different from the start and so can be qualitatively different in their own gene activity.
The substances that Gross studied are maternal messenger RNA’s –products of certain of the maternal genes. He and other biologists studying a wide variety of organisms have found that these particular RNA’s direct, in large part, the synthesis of histones, a class of proteins that bind to DNA. Once synthesized, the histones move into the cell nucleus, where sections of DNA wrap around them to form a structure that resembles beads, or knots, on a string. The beads are DNA segments wrapped around the histones; the string is the intervening DNA. And it is the structure of these beaded DNA strings that guides the fate of the cells in which they are located.
Q. According to the passage, when biologists believed that the cells in the early embryo were undetermined, they made which of the following mistakes?
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Pardeep Singh asked   •  1 hour ago

Read the following information and answer the questions given below it. For selection of films produced before December 2020 for the Bhojpuri film festival, following criteria are given.
1. The film must be submitted to the Bhojpuri Film Development Corporation (BFDC) by 31.10.2020.
2. The production cost of the film should not exceed Rupees Five crores.
3. The director of the film should have passed a three year course either from the Film and Television Institute of India (FTII) or from Satyajit Ray Film & Television Institute.
4. The length of the film should not exceed 150 minutes.
5. The film must have been approved by the film censor board of India.
6. However, if the film fulfils all the above criteria except
(a) criteria 2 above, it must be sent to the finance secretary
(b) criteria 3 above, the director has done at least a one year course from FTII or Satyajit Ray Film & Television Institute, the film is kept as a stand-bye
On the basis of above information and information provided below, decide the course of action in each case. No further information is available. You are not to assume anything.
Mark answer:
  1. if the film is to be selected
  2. if the film is not to be selected
  3. if the film should be sent to the finance secretary
  4. if the film should be kept as a stand-bye
  5. if the data given about the film are not adequate to make a decision.
Q. Film Saajan was produced at the cost of Rupees 2.5 crore. It was submitted to the BFDC on 29th September 2020. The director of the film raj bhimani passed a 3-year course from FTII. Length of film was 120 minutes and has been approved by the censor board of India.
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Sona Devi asked   •  1 hour ago

A passage is followed by questions pertaining to the passage. Read the passage and answer the questions. Choose the most appropriate answer.
Meteorological seasons are reckoned by temperature, with summer being the hottest quarter of the year and winter the coldest quarter of the year. Using this reckoning, the Roman calendar began the year and the spring season on the first of March, with each season occupying three months. In 1780 the Societas Meteorologica Palatina, an early international organization for meteorology, defined seasons as groupings of three whole months. Ever since, professional meteorologists all over the world have used this definition. So, in meteorology for the Northern hemisphere: spring begins on 1 March, summer on 1 June, autumn on 1 September, and winter on 1 December.
Ecologically speaking, a season is a period of the year in which only certain types of floral and animal events happen (e.g.: flowers bloom—spring; hedgehogs hibernate—winter). So, if we can observe a change in daily floral/animal events, the season is changing.
Traditional seasons are reckoned by insolation, with summer being the quarter of the year with the greatest insolation and winter the quarter with the least. In traditional reckoning, the seasons begin at the cross-quarter days. The solstices and equinoxes are the midpoints of these seasons.
In Australia, the traditional aboriginal people defined the seasons by what was happening to the plants, animals and weather around them. This led to each separate tribal group having different seasons, some with up to eight seasons each year. However, most modern Aboriginal Australians follow either four or six meteorological seasons, as do non-Aboriginal Australians.
In India, and in the Hindu calendar, there are six seasons or Ritu: Hemant (pre-winter), Shishira (Winter), Vasanta (Spring), Greeshma (Summer), Varsha (Rainy) and Sharad (Autumn).
Q. Based on the passage, we can infer all the statements, except: 
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Sona Devi asked   •  1 hour ago

Read the passage carefully and answer within the context
A long-held view of the history of the English colonies that became the United States has been that England’s policy toward these colonies before 1763 was dictated by commercial interests and that a change to a more imperial policy, dominated by expansionist militarist objectives, generated the tensions that ultimately led to the American Revolution. In a recent study, Stephen Saunders Webb has presented a formidable challenge to this view. According to Webb, England already had a military imperial policy for more than a century before the American Revolution. He sees Charles II, the English monarch between 1660 and 1685, as the proper successor of the Tudor monarchs of the sixteenth century and of Oliver Cromwell, all of whom were bent on extending centralized executive power over England’s possessions through the use of what Webb calls “garrison government.” Garrison government allowed the colonists a legislative assembly, but real authority, in Webb’s view, belonged to the colonial governor, who was appointed by the king and supported by the “garrison,” that is, by the local contingent of English troops under the colonial governor’s command.
According to Webb, the purpose of garrison government was to provide military support for a royal policy designed to limit the power of the upper classes in the American colonies. Webb argues that the colonial legislative assemblies represented the interests not of the common people but of the colonial upper classes, a coalition of merchants and nobility who favored self-rule and sought to elevate legislative authority at the expense of the executive. It was, according to Webb, the colonial governors who favored the small farmer, opposed the plantation system, and tried through taxation to break up large holdings of land. Backed by the military presence of the garrison, these governors tried to prevent the gentry and merchants, allied in the colonial assemblies, from transforming colonial America into a capitalistic oligarchy.
Webb’s study illuminates the political alignments that existed in the colonies in the century prior to the American Revolution, but his view of the crown’s use of the military as an instrument of colonial policy is not entirely convincing. England during the seventeenth century was not noted for its military achievements. Cromwell did mount England’s most ambitious overseas military expedition in more than a century, but it proved to be an utter failure. Under Charles II, the English army was too small to be a major instrument of government. Not until the war with France in 1697 did William III persuade Parliament to create a professional standing army, and Parliaments price for doing so was to keep the army under tight legislative control. While it may be true that the crown attempted to curtail the power of the colonial upper classes, it is hard to imagine how the English army during the seventeenth century could have provided significant military support for such a policy.
Q. According to the passage, Webb views Charles II as the “proper successor” (line 13) of the Tudor monarchs and Cromwell because Charles II
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Prem Kumar asked   •  1 hour ago

Read the passage carefully and answer within the context
Viruses, infectious particles consisting of nucleic acid packaged in a protein coat (the capsid), are difficult to resist. Unable to reproduce outside a living cell, viruses reproduce only by subverting the genetic mechanisms of a host cell. In one kind of viral life cycle, the virus first binds to the cell’s surface, then penetrates the cell and sheds its capsid. The exposed viral nucleic acid produces new viruses from the contents of the cell. Finally, the cell releases the viral progeny, and a new cell cycle of infection begins. The human body responds to a viral infection by producing antibodies: complex, highly specific proteins that selectively bind to foreign molecules such as viruses. An antibody can either interfere with a virus’s ability to bind to a cell, or can prevent it from releasing its nucleic acid.
Unfortunately, the common cold, produced most often by rhinoviruses, is intractable to antiviral defense. Humans have difficulty resisting colds because rhinoviruses are so diverse, including at least 100 strains. The strains differ most in the molecular structure of the proteins in their capsids. Since disease-fighting antibodies bind to the capsid, an antibody developed to protect against one rhinovirus strain is useless against other strains. Different antibodies must be produced for each strain.
A defense against rhinoviruses might nonetheless succeed by exploiting hidden similarities among the rhinovirus strains. For example, most rhinovirus strains bind to the same kind of molecule (delta-receptors) on a cell’s surface when they attack human cells. Colonno, taking advantage of these common receptors, devised a strategy for blocking the attachment of rhinoviruses to their appropriate receptors. Rather than fruitlessly searching for an antibody that would bind to all rhinoviruses, Colonno realized that an antibody binding to the common receptors of a human cell would prevent rhinoviruses from initiating an infection. Because human cells normally do not develop antibodies to components of their own cells, Colonno injected human cells into mice, which did produce an antibody to the common receptor. In isolated human cells, this antibody proved to be extraordinarily effective at thwarting the rhinovirus. Moreover, when the antibody was given to chimpanzees, it inhibited rhinoviral growth, and in humans it lessened both the severity and duration of cold symptoms.
Another possible defense against rhinoviruses was proposed by Rossman, who described rhinoviruses’ detailed molecular structure. Rossman showed that protein sequences common to all rhinovirus strains lie at the base of a deep “canyon” scoring each face of the capsid. The narrow opening of this canyon possibly prevents the relatively large antibody molecules from binding to the common sequence, but smaller molecules might reach it. Among these smaller, non - antibody molecules, some might bind to the common sequence, lock the nucleic acid in its coat, and thereby prevent the virus from reproducing.
Q. It can be inferred from the passage that the purpose of Colonno’s experiments was to determine whether
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Subhash Chander asked   •  1 hour ago

​​Read the passage carefully and answer within the context
Classical physics defines the vacuum as a state of absence: a vacuum is said to exist in a region of space if there is nothing in it. In the quantum field theories that describe the physics of elementary particles, the vacuum becomes somewhat more complicated. Even in empty space, particles can appear spontaneously as a result of fluctuations of the vacuum. For example, an electron and a positron, or antielectron, can be created out of the void. Particles created in this way have only a fleeting existence; they are annihilated almost as soon as they appear, and their presence can never be detected directly. They are called virtual particles in order to distinguish them from real particles, whose lifetimes are not constrained in the same way, and which can be detected. Thus it is still possible to define that vacuum as a space that has no real particles in it.
One might expect that the vacuum would always be the state of lowest possible energy for a given region of space. If an area is initially empty and a real particle is put into it, the total energy, it seems, should be raised by at least the energy equivalent of the mass of the added particle. A surprising result of some recent theoretical investigations is that this assumption is not invariably true. There are conditions under which the introduction of a real particle of finite mass into an empty region of space can reduce the total energy. If the reduction in energy is great enough, an electron and a positron will be spontaneously created. Under these conditions the electron and positron are not a result of vacuum fluctuations but are real particles, which exist indefinitely and can be detected. In other words, under these conditions the vacuum is an unstable state and can decay into a state of lower energy; i.e., one in which real particles are created.
The essential condition for the decay of the vacuum is the presence of an intense electric field. As a result of the decay of the vacuum, the space permeated by such a field can be said to acquire an electric charge, and it can be called a charged vacuum. The particles that materialize in the space make the charge manifest. An electric field of sufficient intensity to create a charged vacuum is likely to be found in only one place: in the immediate vicinity of a superheavy atomic nucleus, one with about twice as many protons as the heaviest natural nuclei known. A nucleus that large cannot be stable, but it might be possible to assemble one next to a vacuum for long enough to observe the decay of the vacuum. Experiments attempting to achieve this are now under way.
Q. The author’s assertions concerning the conditions that lead to the decay of the vacuum would be most weakened if which of the following occurred?
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Shoukat Ali asked   •  1 hour ago

In this paragraph last sentence that completes the paragraph has been deleted. From the given options chooses the sentence that completes the paragraph in the most appropriate way.
War was also widely seen before 1914 by the upper class across Europe as an assertion of masculine honour, like a duel, as it were, only on a much bigger scale. Duelling was a common way of avenging real or imagined slights to a man’s honour in virtually every European country at the time. Only in Britain had it died out: the point of a duel was to vindicate one’s manly honour by standing unmoving as your opponent fired a bullet at you at twenty or thirty paces, and the invention of modern cricket, in which a man was required to face down a different kind of round, hard object as it hurtled towards him from the other end of the wicket, was a satisfactory(and comfortingly legal) substitute.
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Amar Singh asked   •  1 hour ago

Read the passage carefully and answer within the context
Viruses, infectious particles consisting of nucleic acid packaged in a protein coat (the capsid), are difficult to resist. Unable to reproduce outside a living cell, viruses reproduce only by subverting the genetic mechanisms of a host cell. In one kind of viral life cycle, the virus first binds to the cell’s surface, then penetrates the cell and sheds its capsid. The exposed viral nucleic acid produces new viruses from the contents of the cell. Finally, the cell releases the viral progeny, and a new cell cycle of infection begins. The human body responds to a viral infection by producing antibodies: complex, highly specific proteins that selectively bind to foreign molecules such as viruses. An antibody can either interfere with a virus’s ability to bind to a cell, or can prevent it from releasing its nucleic acid.
Unfortunately, the common cold, produced most often by rhinoviruses, is intractable to antiviral defense. Humans have difficulty resisting colds because rhinoviruses are so diverse, including at least 100 strains. The strains differ most in the molecular structure of the proteins in their capsids. Since disease-fighting antibodies bind to the capsid, an antibody developed to protect against one rhinovirus strain is useless against other strains. Different antibodies must be produced for each strain.
A defense against rhinoviruses might nonetheless succeed by exploiting hidden similarities among the rhinovirus strains. For example, most rhinovirus strains bind to the same kind of molecule (delta-receptors) on a cell’s surface when they attack human cells. Colonno, taking advantage of these common receptors, devised a strategy for blocking the attachment of rhinoviruses to their appropriate receptors. Rather than fruitlessly searching for an antibody that would bind to all rhinoviruses, Colonno realized that an antibody binding to the common receptors of a human cell would prevent rhinoviruses from initiating an infection. Because human cells normally do not develop antibodies to components of their own cells, Colonno injected human cells into mice, which did produce an antibody to the common receptor. In isolated human cells, this antibody proved to be extraordinarily effective at thwarting the rhinovirus. Moreover, when the antibody was given to chimpanzees, it inhibited rhinoviral growth, and in humans it lessened both the severity and duration of cold symptoms.
Another possible defense against rhinoviruses was proposed by Rossman, who described rhinoviruses’ detailed molecular structure. Rossman showed that protein sequences common to all rhinovirus strains lie at the base of a deep “canyon” scoring each face of the capsid. The narrow opening of this canyon possibly prevents the relatively large antibody molecules from binding to the common sequence, but smaller molecules might reach it. Among these smaller, non - antibody molecules, some might bind to the common sequence, lock the nucleic acid in its coat, and thereby prevent the virus from reproducing.
Q. The primary purpose of the passage is to
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