Correct answer: (b) 2 and 3 only
Explanation
- A
1 only
(a) 1 only. Statement 1 claims H-CNG eliminates carbon monoxide. Blending hydrogen in CNG reduces CO; it does not eliminate it. So 1 only is not the key.
- B
2 and 3 only
(b) 2 and 3 only. H-CNG lowers carbon dioxide and hydrocarbon emissions relative to CNG, and trials have used hydrogen up to about 18–20 per cent by volume in city buses. Statement 4 (cheaper than CNG) is false — hydrogen blending raises cost — and statement 1 overclaims elimination of CO. 2-and-3 is the official key.
- C
4 only
(c) 4 only. H-CNG is not cheaper than CNG, so 4 only is not the key.
- D
1, 2, 3 and 4
(d) 1, 2, 3 and 4. Statements 1 and 4 fail, so all-four is not the key.
Summary. Official key is (b) 2 and 3 only. Delhi trials of hydrogen-enriched CNG showed cuts in CO2 and hydrocarbons with a hydrogen blend around one-fifth by volume. Carbon monoxide is reduced, not wiped out, and the fuel is costlier than plain CNG. Honour the stored letter (b).
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