Test: Assertion & Reason - 1 - UPSC MCQ

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.

Earth is indeed the only planet known to have life. However, the presence of an atmosphere with oxygen, nitrogen, and carbon dioxide is not the sole reason for life.

• While Earth’s atmosphere is crucial for sustaining life, other factors also contribute, such as the presence of water and suitable temperatures.
• The atmosphere itself is important, but it is not the complete explanation for Earth's ability to support life.

Therefore, both the Assertion and Reason are true, but the reason is not the correct explanation of the assertion.

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

• Diamond is hard due to its rigid three dimensional structure and so, it is used for cutting glass.
• Refractive index of diamond is high and this gives it greater transparency and brilliance.

Rainfall in Tamil Nadu is caused by the retreating monsoons which occur in winter.

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.

• 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.

Bronze is an alloy of copper and tin. It is resistant to corrosion and so it is used to make statues.

• Assertion (A): Telephone wires sag more in summer. This is true because, in hot weather, the wires expand due to the heat, which causes them to sag more.
• Reason (R): They expand due to summer heat. This is also true as heat causes the metal wires to expand, which increases their length and leads to sagging.

So, both the assertion and reason are true, and the reason correctly explains the assertion.

Thus, the correct answer is: e) Both A and R are true and R is the correct explanation of A.

• 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.