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: I. The main advantage of the use of H-CNG is the elimination of carbon monoxide emissions. II. H-CNG as fuel reduces carbon dioxide and hydrocarbon emissions. III. Hydrogen up to one-fifth by volume can be blended with CNG as fuel for buses. IV. H-CNG makes the fuel less expensive than CNG. Which of the statements given above is/are correct?

Check each statement against what H-CNG actually does. Statement I is wrong: adding hydrogen cuts carbon monoxide and other pollutants, but it does not eliminate CO, because the CNG part still burns and produces some. Statement II is correct: hydrogen burns faster and more completely, so CO2 and unburnt hydrocarbons fall. Statement III is correct: blends up to about 20% hydrogen by volume are considered workable in CNG engines with limited modification, and the Indian bus trials used around 18%. Statement IV is wrong: producing, storing and blending hydrogen adds cost, so H-CNG is not cheaper than CNG.

So the answer is B. The core concept is hydrogen as a transition fuel for cleaner urban transport. It links to the push for alternative fuels and the Auto Fuel Policy, which is useful for GS-III (energy and environment) and for Mains answers on urban air quality.

Trap: Aspirants tick statement I because "elimination" sounds like a strong benefit. The exam tests the difference between reduction and elimination of emissions.