Test: Science and Technology- 2 - UPSC MCQ

• Dry ice, sometimes referred to as "Cardice" or as "card ice" is the solid form of carbon dioxide. 
• It is used primarily as a cooling agent. 
• Its advantages include lower temperature than that of water ice and not leaving any residue (other than incidental frost from moisture in the atmosphere). 
• It is useful for preserving frozen foods, ice cream, etc., where mechanical cooling is unavailable.

• The effects of forces of the same magnitude on different areas are different. When the person stands on loose sand, the force, that is, the weight of his body is acting on an area equal to the area of his feet. When he lies down, the same force acts on an area equal to the contact area of his whole body, which is larger than the area of his feet. In both cases, the force exerted on the sand is the weight of his body and the force is acting perpendicular to the surface of the sand. The force acting on an object perpendicular to the surface is called thrust. The effect of thrust on sand is larger while standing than while lying. The thrust on the unit area is called pressure. 
• Pressure = Thrust/Area 
• Thus, higher pressure is exerted by the body on the sand while standing and the person goes down deeper into it as compared to when he is lying down.

• Most animals use “body language” as well as sound and smell in order to communicate with one another. Chimpanzees greet each other by touching hands. Male fiddler crabs wave their giant claw to attract female fiddler crabs. White-tailed deer show alarm by flicking up their tails. 
• Many animals communicate by smell: they release pheromones (airborne chemicals) to send messages to others. Pheromones play an important part in reproduction and other social behavior. They are used by many animals, including insects, wolves, deer etc. 
• Bees dance when they have found nectar. The scout bee will dance in the hive, and the dance directs other bees to the location of the nectar. 
• Animals use sound to warn others to stay out of its territory and also to attract a mate. They make at least twenty five different sounds which include growling, squawking, squealing, cooing, and rattling. 
• Hence option (d) is the correct answer.

• The significance of mitosis in the living world is:
  • Growth of the body: Growth of the body of a living being takes place by mitotic division. A unicellular zygote is transformed to a human body. Hence, statement 2 is correct.
  • Maintaining equality of chromosome number: By this division the number and properties of a chromosome in each cell of a multicellular body remains constant.
  • Keeping the size and shape constant: By this division the definite shape and size of the cell remains constant.
  • Healing of injuries: By producing new cells this process repairs the various types of damage of multicellular organisms. Hence, statement 1 is correct.
  • Formation of sex organs: By this process sex organs are formed. As a result, continuity of reproductive sequence is maintained.
• Every living being has a definite number of chromosomes. In human beings there are 23 pairs of chromosome. Among them 22 pairs are similar in both male and female, these are Autosomes, AA. Members of the remaining pair of chromosome are different in male and female. This pair of chromosome determines the sex of human beings. Hence, statement 3 is not correct.

• Multispectral imagery is produced by sensors that measure reflected energy within several specific sections (also called bands) of the electromagnetic spectrum. Multispectral sensors usually have between 3 and 10 different band measurements in each pixel of the images they produce. Examples of bands in these sensors typically include visible green, visible red, near-infrared, etc. Landsat, Quickbird, and Spot satellites are well-known satellite sensors that use multispectral sensors.
• Hyperspectral sensors measure energy in narrower and more numerous bands than multispectral sensors. Hyperspectral images can contain as many as 200 (or more), contiguous spectral bands. The numerous narrow bands of hyperspectral sensors provide a continuous spectral measurement across the entire electromagnetic spectrum and therefore are more sensitive to subtle variations in reflected energy. Images produced from hyperspectral sensors contain much more data than images from multispectral sensors and have a greater potential to detect differences among land and water features.
• Hyperspectral imaging has been widely used in mineral exploration and mapping, vegetation classification (identification of trees in forests) and environment analysis, etc. Hence options 1 and 2 are correct.
• Bat detectors use sound frequency converters to convert the ultrasound frequencies into audible frequencies. They do not use hyperspectral imaging. Hence option 3 is not correct.

• Hypermetropia is also known as far-sightedness. It is a form of refractive error in which parallel rays of light coming from infinity are focused behind the light-sensitive layer of the retina when the eye is at rest. Hence statement 1 is correct.
• A person with hypermetropia can see distant objects clearly but cannot see nearby objects distinctly. The near point for the person is farther away from the normal near point. This is because in hypermetropia, the cornea is flatter or the axial length is too short. Therefore, the images do not focus by the time they reach the retina. Hence statement 2 is correct.
• This defect arises either because: the focal length of the eye lens is too long or the eyeball has become too small. This defect can be corrected by using a convex (outward facing) lens of appropriate power. Eyeglasses with converging lenses provide the additional focusing power required for forming the image on the retina. Hence statement 3 is not correct.

Refraction is the bending of a wave when it enters a medium where its speed is different. The refraction of light when it passes from a fast medium to a slow medium bends the light ray toward the normal to the boundary between the two media. The amount of bending depends on the indices of refraction of the two media. Some of the common examples are:

• A straw in a glass with water looks bent or broken.
• A swimming pool appears shallower than it actually is. This is because the light from the pool is refracted away from the normal when moving from water to the air.
• The setting sun looks oval in shape because the light from the sun is refracted at a different rate when passes through the atmosphere.
• The light of stars is refracted when passes through the different region in the atmosphere. The angle of refraction varies a little from time to time. As a result, the stars look twinkling.

One Future Alliance’ (OFA)

• It is a voluntary initiative proposed by the G20 India Presidency with support from UNDP and its knowledge partners.
• It aims to bring together governments, the private sector, academic and research institutions, donor agencies, civil society organizations and other relevant stakeholders and existing mechanisms to synergize global efforts in the Digital Public infrastructure (DPI ) ecosystem. Digital Public Infrastructure
• DPI refers to platforms such as identification (ID), payment and data exchange systems that help countries deliver vital services to their people.
• DPI is a combination of Networked open technology standards built for public interest, Enabling governance, and A community of innovative and competitive market players working to drive innovation, especially across public programmes

• A new Chinese Earth observation satellite named “Ziyuan-1 02E” was launched into space by China. Hence pair 1 is correctly matched.
• The satellite, called Ziyuan-1 02E, has been equipped with a high-resolution infrared camera, a long- wavelength infrared camera and a multi-spectrum imager.
• The satellite is designed for an eight-year lifespan in Earth orbit. It was launched with the objective of mapping the Earth’s surface in high resolution to explore the natural resources. Data from satellites will be used to alert for environmental disasters and monitor water quality.
• China boosts Earth-observation abilities with 2 Gaofen satellites. Hence pair 2 is not correctly matched. The two new satellites launched on separate rockets and from different space centres, but they share a name, Gaofen ("high resolution"). While both will observe the Earth, each will have different roles and users.
• Recently, The third test flight of the Angara A5 rocket took off from Plesetsk Cosmodrome in northwestern Russia. Hence pair 3 is correctly matched. The launcher reached low Earth orbit but was unable to go higher as planned due to an engine failure in its upper-stage Persei booster.

• A cookie (called an Internet or Web cookie) is the term given to describe a type of message that is given to a web browser by a web server. The main purpose of a cookie is to identify users and possibly prepare customized Web pages or to save site login information for you.
• When you enter a website using cookies, you may be asked to fill out a form providing personal information; like your name, email address, and interests. This information is packaged into a cookie and sent to your Web browser, which then stores the information for later use. The next time you go to the same Web site, your browser will send the cookie to the Web server. The message is sent back to the server each time the browser requests a page from the server. 
• A web server has no memory so the hosted website you are visiting transfers a cookie file of the browser on your computer's hard disk so that the site can remember who you are and your preferences. This message exchange allows the Web server to use this information to present you with customized Web pages. So, for example, instead of seeing just a generic welcome page you might see a welcome page with your name on it.
• Hence option (c) is the correct answer.

• Augmented Reality blends virtual reality and real life, but users continue to be in touch with the real world while interacting with virtual objects around them, so they can distinguish between the two.
• Virtual Reality creates an entirely fabricated world, that users would find it difficult to tell the difference between what is real and what is not. Hence, statement 1 is correct.
• VR is usually possible by wearing a VR helmet or goggles while AR does not require users to wear special glasses. Hence, statement 2 is not correct.

• Composition of Regular Crackers – A traditional firecracker comprises of six key elements:
• Fuel: Mainly Charcoal or Thermite are present in them all
• Oxidising Agents: Nitrates and Chlorates which produce oxygen inside the cracker
• Reducing Agents: Something like sulphur, which can burn the oxygen present in the firecracker
• Regulators: To ensure the speed and intensity with which a cracker bursts
• Coloring Agents: Multiple colours appear when a cracker bursts, this role is played by the colouring agents. Given below are the elements which provide different colours:
• Strontium salts – Red Colour, hence pair 1 is correctly matched.
• Burning of metals – White Colour
• Sodium salts – Yellow Colour, hence pair 3 is correctly matched.
• Barium salts – Green Colour
• Calcium Salts – Orange Colour, hence pair 4 is not correctly matched.
• Copper Salts – Blue Colour, hence pair 2 is not correctly matched.
• Binders: All the components of the firecracker require a medium which can bind them

A nephron is the basic structural and functional unit of the kidney. They are the microscopic structure composed of a renal corpuscle and a renal tubule.

• Structure of Nephron
  • The mammalian nephron is a long tube-like structure, its length varying from 35–55 mm long. At one end, the tube is closed, folded and expanded, into a double-walled, cuplike structure called the Bowman‘s capsule or renal corpuscular capsule, which encloses a cluster of microscopic blood vessels called the glomerulus. This capsule and glomerulus together constitute the renal corpuscle.
• Functions of Nephron
  • The primary function of the nephron is removing all waste products including the solid wastes, and other excess water from the blood, converting blood into urine, reabsorption, secretion, and excretion of numerous substances.
  • As the blood passes through the glomerulus with high pressure, the small molecules are moved into the glomerular capsules and travel through a winding series of tubules.
  • The cell present in each tube absorbs different molecules excluding the glucose, water, and other beneficial molecules which are called ass ultrafiltrate. As the ultrafiltrate molecules travel down the tubules they become more and more hypertonic, which results in more amount of water to be extracted from the ultrafiltrate before it exits the nephrons.
  • The blood surrounding the nephron travels back into the body through the renal blood vessels, which are free of toxins and other excess substances. The obtained ultrafiltrate is urine, which travels down via the collecting duct to the bladder, where it will be stored and released through the urethra.

What is a clone?

• A clone is a living organism (such as a plant or animal), which shares the same genetic information as another organism. However, their characteristics can be affected by random mutations which occur in their DNA during development in the womb or by the environment that they grow up in, so, although clones have the same DNA, they may not look the same or behave in the same way.
• While some clones can be found in nature, it is also possible for scientists to create a clone or identical copy of an organism. It is important to understand that a cloned animal is not the same as a genetically modified animal. Hence, statement 1 is correct.
• A cloned animal shares the same DNA as another animal, while a genetically modified animal has had a change made to its DNA, but does not share its DNA with any other animals. Hence, statement 2 is correct.
• Scientists can also use bacteria or viruses to replicate or clone individual DNA sequences that they are interested in. This is known as molecular or DNA cloning.

What Is an Adult Stem Cell?

• Adult stem cells, like all stem cells, share at least two characteristics.
• First, they can make identical copies of themselves for long periods of time; this ability to proliferate is referred to as long-term self-renewal. Hence, statement 1 is correct.
• Second, they can give rise to mature cell types that have characteristic morphologies (shapes) and specialized functions.
• Typically, stem cells generate an intermediate cell type or types before they achieve their fully differentiated state. The intermediate cell is called a precursor or progenitor cell. Progenitor or precursor cells in fetal or adult tissues are partly differentiated cells that divide and give rise to differentiated cells. Such cells are usually regarded as "committed" to differentiating along a particular cellular development pathway, although this characteristic may not be as definitive as once thought.
• Adult stem cells are rare. Their primary functions are to maintain the steady-state functioning of a cell—called homeostasis—and, with limitations, to replace cells that die because of injury or disease. Hence, statement 2 is correct.
• Furthermore, adult stem cells are dispersed in tissues throughout the mature animal and behave very differently, depending on their local environment. In contrast, stem cells in the small intestine are stationary and are physically separated from the mature cell types they generate.
• Unlike embryonic stem cells, which are defined by their origin (the inner cell mass of the blastocyst), adult stem cells share no such definitive means of characterization. In fact, no one knows the origin of adult stem cells in any mature tissue. Some have proposed that stem cells are somehow set aside during fetal development and restrained from differentiating.
• Most of the information about adult stem cells comes from studies of mice. The list of adult tissues reported containing stem cells is growing and includes bone marrow, peripheral blood, brain, spinal cord, dental pulp, blood vessels, skeletal muscle, epithelia of the skin and digestive system, cornea, retina, liver, and pancreas.
• In order to be classified as an adult stem cell, the cell should be capable of self-renewal for the lifetime of the organism.
• Ideally, adult stem cells should also be clonogenic. In other words, a single adult stem cell should be able to generate a line of genetically identical cells, which then gives rise to all the appropriate, differentiated cell types of the tissue in which it resides.

In News : The UK has rejoined the flagship Horizon Europe research programme

• Along with Horizon Europe, the UK has joined Copernicus.
• Statement 1 is correct : Horizon Europe is the world’s biggest civil research and innovation programme
• It is open to EU member states and countries that associate to the programme, as the UK has now done after leaving it due to Brexit.
• The funding supports international collaborations focused on a wide range of issues, from cancer and infectious diseases to the climate crisis, food security, artificial intelligence and robotics.
• Statement 2 is not correct : Copernicus is the Earth observation component of the European Union’s Space programme, looking at our planet and its environment to benefit all European citizens.
• It offers information services that draw from satellite Earth Observation and in-situ (non-space) data.

• NASA’s James Webb Space Telescope in its study of K2-18 b discovered the presence of carbon dioxide and methane
• K2-18 b is a super Earth exoplanet that orbits an M-type star. It lies 120 light years from earth and orbits the cool dwarf star K2-18 a.
• It is 8.6 times as massive as Earth and the size lies that of between earth and Neptune.

The Oldest fossils of a plant-eating dinosaur have been found in the Thar desert near the Jaisalmer Basin, Rajasthan by the Geological Survey of India. Tharosaurus indicus

• The scientists discovered the remains of a Sauropod dinosaur, which is the same clade as the long-necked herbivores in Jurassic Park – these happened to be the oldest known fossils of this particular kind of sauropod.
• The fossils belong to the family Dicraeosauridae and from the superfamily Diplodocoidea.
• These are the first Dicraeosaurid sauropods to have been found in India.
• The scientists named the dinosaur Tharosaurus indicus, with Tharo deriving from the Thar desert; saurus from the Greek ‘sauros’, or lizard; and indicus from its Indian origin.
• At 167 million years old, they are the oldest known Diplodocoid fossils in the world.
• However, members of the Dicraeosauridae family of sauropods – to which Tharasaurus belongs – were not nearly as large. This family was unique: its members were smaller and had shorter necks and tails compared to the other long-necked sauropods.

Statement 1 is not correct: Asteroids, sometimes called minor planets, are rocky, airless remnants left over from the early formation of our solar system about 4.6 billion years ago.

• It likely formed in the Main Asteroid Belt between Mars and Jupiter. The belt is estimated to contain between 1.1 and 1.9 million asteroids larger than 1 kilometre in diameter, and millions of smaller ones.

Statement 2 is not correct: Japan, and the USA are the only countries to bring back asteroid samples.

• A sample from the Asteroid Ryugu, having a rich complement of organic molecules, delivered by Japan’s Hayabusa2 spacecraft.
• The Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft of NASA released the sample from the Bennu asteroid in the Utah desert of the USA.

Statement 3 is correct: Asteroid Bennu is a small, near-Earth asteroid that passes close to Earth about every six years.

• Bennu is expected to come dangerously close to Earth in 2182.
• The data collected by Osiris-Rex will help with asteroid-deflection efforts.

• Statement 1 is correct: Mars has a thin atmosphere composed mainly of carbon dioxide.
• Statement 2 is not correct: Mars has two moons, Phobos and Deimos. Saturn has 146 moons in its orbit. The giant moon is Titan and the small moon is Enceladus.
• Statement 3 is correct: Mars is known as the Red Planet because iron minerals in the Martian soil oxidize, or rust, causing the soil and atmosphere to look red.

• Endoplasmic reticulum and Ribosomes.
• Ribosomes are the factories of protein synthesis. They are 70S type in prokaryotes and 80S type in Eukaryotes. When Ribosomes are attached to Endoplasmic reticulum (ER), it is called Rough ER which helps in protein synthesis.
• Hence option (b) is the correct answer.

• The programme called Women’s Involvement in Science and Engineering Research (WISER) program was launched by Indo-German Science & Technology Centre (IGSTC) for encouraging women researchers in joint R&D projects. Hence statement 2 is correct.
• It is launched to promote women in the field of research and development by lateral entry.
• This programme was launched in addition to the ongoing flagship 2+2 program of the IGSTC.
• This program by IGSTC, a joint initiative of the Department of Science and Technology (DST), Government of India and the Federal Ministry of Education and Research (BMBF), Government of Germany,
• It will support women scientists holding regular/long term research positions in academia or research institutes/industries.
• Involvement in the program will be possible through lateral entry. There is neither requirement of break-in-career nor any age limit, and it will enable easy participation. Hence statement 1 is not correct.

• Recombinant DNA (rDNA) molecules are DNA molecules formed by laboratory methods of genetic recombination i.e. molecules of DNA from two different species that are inserted into a host organism to produce new genetic combinations that are of value to science, medicine, agriculture, and industry.
• Applications of Recombinant DNA:
  • Through recombinant DNA techniques, bacteria have been created that are capable of synthesizing human insulin, human growth hormone, alpha interferon, hepatitis B vaccine, and other medically useful substances. Hence option 1 is correct.
  • Recombinant DNA technology also can be used for gene therapy, in which a normal gene is introduced into an individual’s genome in order to repair a mutation that causes a genetic disease.
  • The ability to obtain specific DNA clones using recombinant DNA technology has also made it possible to add the DNA of one organism to the genome of another. The added gene is called a transgene, which can be passed to progeny as a new component of the genome. The resulting organism carrying the transgene is called a transgenic organism or a genetically modified organism (GMO). In this way, a “designer organism” is made that contains some specific change required for an experiment in basic genetics or for improvement of some commercial strain.
  • Genetically transformed plants which contain foreign genes are called transgenic plants. Resistance to diseases, insects and pests, herbicides, drought; metal toxicity tolerance; induction of male sterility for plant breeding purpose; and improvement of quality can be achieved through this recombinant DNA technology. BT-cotton, resistant to bollworms is a glaring example. Hence option 2 is correct.
  • Recombinant DNA technology has provided a broad range of tools to help physicians in the diagnosis of diseases. Most of these involve the construction of probes: short Segments of single-stranded DNA attached to a radioactive or fluorescent marker. Such probes are now used for the identification of infectious agents, for instance, food poisoning Salmonella, hepatitis virus, HIV, etc. Hence option 3 is correct.
  • In industries, recombinant DNA technology will help in the production of chemical compounds of commercial importance, improvement of existing fermentation processes, and production of proteins from wastes. This can be achieved by developing more efficient strains of microorganisms. Specially developed microorganisms may be used even to clean up the pollutants. Hence option 4 is correct.

• The term "founder effect" refers to the observation that when a small group of individuals breaks off from a larger population and establishes a new population, chance plays a large role in determining which alleles (a variant form of a gene) are represented in the new population. The particular alleles may not be representative of the larger population. As the new population grows, the allele frequencies will usually continue to reflect the original small group.
• A founder effect occurs when a new colony is started by a few members of the original population. This small population size means that the colony may have:
  • reduced genetic variation from the original population.
  • a non-random sample of the genes in the original population.
• Hence option (a) is the correct answer

Quantum Computing:

• It promises more speed and more efficient problem-solving abilities, challenging the boundaries set by classical, conventional computing.
• A quantum computer has the ability to solve some problems much faster than a classical computer that establishes quantum computers as superior machines, i.e. Quantum supremacy.
• A researcher has shown the ‘Quantum Complexity Theory’ that one class of mathematical problems can be solved only by quantum computers, not classical computers. Quantum Complexity Theory:
• There are computational barriers to classical computers in comparison to quantum computers.
• It challenges the extended Church-Turing thesis, which is the idea that classical computers can efficiently simulate any physical process.

• The main use of litmus is to test whether a solution is acidic or basic. Light Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic or alkaline conditions, with the color change occurring over the pH range 4.5–8.3 at 25 °C (77 °F). The neutral litmus paper is purple. Lemon Juice and Orange Juice are acidic in nature and thus they turn the Light Blue litmus paper into the red. Vinegar is acidic. White distilled vinegar, the kind best suited for household cleaning, typically has a pH of around 2.5.
• Hence the correct option is (d) Sodium bicarbonate, otherwise known as baking soda, has a pH level, of around 8.4, and it is still alkaline in nature. Human blood has a normal pH range of 7.35 to 7.45. This means that blood is naturally slightly alkaline or basic. Hence both do not have any effect on the Light Blue litmus paper. Litmus can also be prepared as an aqueous solution that functions similarly. Under acidic conditions, the solution is red, and under alkaline conditions, the solution is blue.

Athlete‘s foot‖ is a disease caused by  ̳Tinea pedis‘, a fungal species. It grows well in the moist skin between toes and the infected skin may become itchy and red.

ELISA test: An enzyme-linked immunosorbent assay, also called ELISA or EIA, is a test that detects and measures antibodies in your blood. This test can be used to determine if you have antibodies related to certain infectious conditions. Antibodies are proteins that your body produces in response to harmful substances called antigens. An ELISA test may be used to diagnose:

• HIV, which causes AIDS
• Lyme disease o Pernicious anemia
• Rocky Mountain spotted fever
• Rotavirus
• Squamous cell carcinoma
• Syphilis. Hence option (d) is the correct answer.
• Toxoplasmosis
• Varicella-zoster virus, which causes chickenpox and shingles
• Zika virus ELISA is often used as a screening tool before more in-depth tests are ordered. A doctor may suggest this test if you‘re having signs or symptoms of the conditions above. Your doctor may also order this test if they want to rule out any of these conditions. How is the test performed?
• The ELISA test involves taking a sample of your blood. First, a healthcare provider will cleanse your arm with an antiseptic. Then, a tourniquet, or band, will be applied around your arm to create pressure and cause your veins to swell with blood. Next, a needle will be placed in one of your veins to draw a small sample of blood. When enough blood has been collected, the needle will be removed and a small bandage will be placed on your arm where the needle was. You‘ll be asked to maintain pressure at the site where the needle was inserted for a few minutes to reduce blood flow.
• HIV: The human immunodeficiency virus (HIV) targets cells of the immune system, called CD4 cells, which help the body respond to infection. Within the CD4 cell, HIV replicates and in turn, damages and destroys the cell. Without effective treatment of a combination of antiretroviral (ARV) drugs, the immune system will become weakened to the point that it can no longer fight infection and disease. Pernicious anemia: Anemia is a medical condition in which the blood is low in normal red blood cells. Pernicious anemia is one cause of vitamin B-12 deficiency anemia. It‘s thought mainly to be caused by an autoimmune process that makes a person unable to produce a substance in the stomach called intrinsic factor. This substance is needed to absorb dietary vitamin B-12 in the small intestine. This type of anemia is called ―pernicious‖ because it was once considered a deadly disease. This was due to the lack of available treatment. Syphilis: Syphilis is a chronic infectious disease caused by the spirochaete Treponema pallidum. Syphilis is usually transmitted by sexual contact or from mother to infant, although endemic syphilis is transmitted by non-sexual contact in communities living under poor hygiene conditions.
• Rotavirus: Rotaviruses are the most common cause of severe diarrhoeal disease in young children throughout the world. o Although rotavirus infections are unpleasant, you can usually treat this infection at home with extra fluids to prevent dehydration. Occasionally, severe dehydration requires intravenous fluids in the hospital. Dehydration is a serious complication of rotavirus and a major cause of childhood deaths in developing countries.
• Good hygiene, such as washing your hands regularly, is important. But vaccination is the best way to prevent rotavirus infection.
• Symptoms A rotavirus infection usually starts within two days of exposure to the virus. Initial symptoms are a fever and vomiting, followed by three to eight days of watery diarrhea. The infection can cause abdominal pain as well. Lyme Borreliosis (Lyme disease): The spirochaete Borrelia burgdorferi, of which there are several different serotypes.
• Infection occurs through the bite of infected ticks, both adults and nymphs, of the genus Ixodes.
• The disease usually has its onset in summer. Early skin lesions have an expanding ring form, often with a central clear zone. Fever, chills, myalgia and headache are common. Meningeal involvement may follow. Central nervous system and other complications may occur weeks or months after the onset of illness. Arthritis may develop up to 2 years after onset.

The rusting of iron can be prevented by painting, oiling, greasing, galvanizing, chrome plating, anodizing or making alloys. Galvanization is a method of protecting steel and iron from rusting by coating them with a thin layer of zinc. The galvanized article is protected against rusting even if the zinc coating is broken. Alloying is a very good method of improving the properties of a metal. We can get the desired properties by this method. Chrome plating (less commonly chromium plating), often referred to simply as chrome, is a technique of electroplating a thin layer of chromium onto a metal object. The chromed layer can be decorative, provide corrosion resistance, ease cleaning procedures, or increase surface hardness. Anodising is an electrolytic process for producing thick oxide coatings, usually on aluminium and its alloys. The oxide layer is typically 5 to 30μm in thickness and is used to give improved surface resistance to wear and corrosion, or as a decorative layer. Hence the correct option is (c).

Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles (neutrons or protons). The main fuels used in nuclear fusion are deuterium and tritium, both heavy isotopes of hydrogen. Deuterium constitutes a tiny fraction of natural hydrogen, only 0,0153%, and can be extracted inexpensively from seawater. Tritium can be made from lithium, which is also abundant in nature. Helium-3 (He3) is a gas that has the potential to be used as a fuel in future nuclear fusion power plants. There is very little helium-3 available on the Earth. However, there are thought to be significant supplies on the Moon. Zirconium is a lustrous, grey-white, strong transition metal that closely resembles hafnium and, to a lesser extent, titanium. It is not a nuclear fusion fuel.