UPSC Prelims 2003 · General Studies

Question 106: Environment and Ecology

Assertion (A): Coal-based thermal power stations contribute to acid rain. Reason (R): Oxides of carbon are emitted when the coal burns.

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 (b).

Coal-fired power stations release sulphur dioxide and nitrogen oxides, which turn into sulphuric and nitric acids in the atmosphere and cause acid rain, so A is true. Burning coal also gives off oxides of carbon, so R is true, but carbon dioxide does not cause acid rain in any significant way, so R does not explain A.

A. Sulphur dioxide and nitrogen oxides from coal burning cause acid rain.
R. Coal burning does emit oxides of carbon, but they are not the cause of acid rain.

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) R is true but is not the explanation: acid rain comes from sulphur and nitrogen oxides.
(b) Correct: both true, and R is not the explanation.
(c) R is true, so 'R false' fails.
(d) A is true, so 'A false' fails.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2003, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.