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. 2. H-CNG as fuel reduces carbon dioxide and hydrocarbon emissions. 3. Hydrogen up to one-fifth by volume can be blended with CNG as fuel for buses. 4. H-CNG makes the fuel less expensive than CNG. Which of the statements given above is/are correct?

Statements 2 and 3 are correct because H-CNG reduces CO2 and hydrocarbon emissions compared to pure CNG, and the standard blending ratio for existing engines is approximately 18-20% (one-fifth) hydrogen by volume. Statement 1 is the most tempting error; while H-CNG significantly reduces carbon monoxide (by up to 70%), it does not "eliminate" it entirely, and statement 4 is false as H-CNG is currently more expensive to produce than CNG. The core concept tested is the technical feasibility and environmental benefits of alternative green fuels in the transport sector.