Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): Earth is the only planet known to have life.
Reason (R): Earth has an atmosphere which is a mixture of oxygen, nitrogen and carbon dioxide.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Both (A) and (R) are correct but (R) is not the correct explanation of (A)
Assertion (A) — True. The Earth is the only planet on which life is known; no life has been found anywhere else so far.
Reason (R) — True. The Earth’s air is a mixture of gases: about 78% nitrogen and 21% oxygen, with small amounts of argon, carbon dioxide and other gases.
Does (R) explain (A)? No. Life on the Earth depends on several conditions together: liquid water, a suitable range of temperature (from its distance from the Sun), the oxygen and the ozone layer of the air. A list of the gases in the air does not by itself explain why life exists only here; Venus and Mars, for example, also have atmospheres with carbon dioxide and nitrogen but no known life.