2019 GS Paper I, all questions

UPSC Prelims 2019 · GS Paper I

Question 43: Environment and Ecology

In the context of proposals to the use of hydrogen-enriched CNG (H-CNG) as fuel for buses in public transport, consider the following statements :

  1. 1.The main advantage of the use of H-CNG is the elimination of carbon monoxide emissions.
  2. 2.H-CNG as fuel reduces carbon dioxide and hydrocarbon emissions.
  3. 3.Hydrogen up to one-fifth by volume can be blended with CNG as fuel for buses.
  4. 4.H-CNG makes the fuel less expensive than CNG.

Which of the statements given above is/are correct?

a1 only
b2 and 3 only
c4 only
d1, 2, 3 and 4

AnswerUPSC’s answer is (b).

Statements 2 and 3 are correct. H-CNG, which is CNG blended with hydrogen, reduces carbon monoxide, carbon dioxide and hydrocarbon emissions, and hydrogen up to about one-fifth by volume can be blended for buses. It does not eliminate carbon monoxide, only cuts it. It also does not make the fuel cheaper than CNG, because hydrogen is costly to produce.

  • 1. H-CNG cuts carbon monoxide but does not eliminate it.
  • 2. It reduces carbon dioxide and hydrocarbon emissions.
  • 3. Up to about one-fifth hydrogen by volume can be blended.
  • 4. Hydrogen is costly, so H-CNG is not cheaper than CNG.

How you could have got this

  1. If you were sure statement 1 is not correct, (a) and (d) go: each of them includes 1.

    What you needed to know: H-CNG cuts carbon monoxide but does not eliminate it.

  2. Then, if you were sure statement 2 is correct, (c) goes: it leaves 2 out.

    What you needed to know: It reduces carbon dioxide and hydrocarbon emissions.

Only (b) is left. You didn’t need statements 3 or 4.

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) H-CNG reduces carbon monoxide but does not eliminate it.
  • (b) Correct: statements 2 and 3 hold.
  • (c) H-CNG is not cheaper than CNG.
  • (d) Statements 1 and 4 are false.

Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2019, General Studies Paper I, Series A. The paper on upsc.gov.in.