UPSC Prelims 2005 · General Studies

Question 84: Geography

Assertion (A): Existence of human life on Venus is highly improbable. Reason (R): Venus has extremely high level of carbon dioxide in its atmosphere.

aBoth A and R are individually true and R is the correct explanation of A

bBoth A and R are individually true but R is not the correct explanation of A

cA is true but R is false

dA is false but R is true

AnswerThe answer is (a).

Venus's atmosphere is about 96% carbon dioxide, which traps heat in a runaway greenhouse effect: the surface is near 460°C and the pressure about 90 times Earth's. Such conditions make human life impossible, so A is true, R is true, and R explains A. Remember Venus as the hottest planet, hotter than Mercury.

A. Human life on Venus is impossible given its heat and pressure.
R. Venus's atmosphere is mostly carbon dioxide, giving an intense greenhouse effect.

How you could have got this

If you were sure statement 1 is correct, (d) goes. Then judge the second statement; if it is correct too, decide whether it explains the first.

This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.

Which options go is worked out from UPSC’s key and the options, not by a model.

Why each option is right or wrong

(a) Correct: both true and R explains A.
(b) R does explain A, so this is wrong.
(c) R is true, so this is wrong.
(d) A is true, so this is wrong.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2005, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.