Test: Assertion & Reason - 1 - CAT MCQ

Graphite possesses a layer structure with two successive layers held by weak forces and able to slide over one another.

So, graphite is slippery and this property finds its use as a lubricant.

In graphite, each carbon atom is linked to three carbon atoms while one electron in the carbon atom is delocalized. So, graphite has free electrons.

The metal of telephone wires expands in summer and the wires become loose. So, they sag.

A vaccine contains the inactivated germs of the disease.

But the AIDS virus changes its genetic code and so on vaccine has been invented for it.

Group O blood carries no antigen on their cells and do not manufacture antibodies against other blood types. This blood can be safely administered to people with other blood groups.

So, group O people are called universal donors. A person with blood group AB is a universal recipient.

Explanation: Earth is indeed the only planet known to have life. However, the reason given is incorrect. Earth does have an atmosphere which is a mixture of oxygen, nitrogen, and carbon dioxide. This atmosphere, along with other factors like the presence of liquid water and suitable temperature range, makes Earth conducive to supporting life.

The handles of pressure cookers are made of ebonite because it being a bad conductor of heat, does not heat up.

An atom contains the positively charged protons and an equal number of negatively charged electrons. So, it is neutral.

However, it is true that neutrons in the nucleus of an atom are neutral.

Due to higher density of sea water, the upthrust produced by the sea water on the ship is greater as compared to that produced by river water.

Assertion (A): Clothes are not washed properly in hard water. → True

Clothes are not washed properly in hard water because it does not form lather with soap.

Reason (R): Hard water contains many minerals. → True

Calcium and magnesium dissolved in water are the two most common minerals that make water "hard." The degree of hardness becomes greater as the calcium and magnesium content increases and is related to the concentration of multivalent cations dissolved in the water.

Both A and R are true, but R is not the correct explanation of A.