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.The main advantage of the use of H-CNG is the elimination of carbon monoxide emissions

1. 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.

2. 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.

3. C

   4 only

   (c) 4 only. H-CNG is not cheaper than CNG, so 4 only is not the key.

4. 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).