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?

1. Statement 1 is incorrect. The main advantage of using H-CNG (hydrogen-enriched CNG) is a significant reduction in carbon monoxide emissions compared to CNG, but not complete elimination. 2. Statement 2 is correct. Blending hydrogen with CNG improves combustion efficiency. This leads to lower emissions of carbon dioxide (due to less carbon per unit energy) and unburnt hydrocarbon emissions. 3. Statement 3 is correct. Pilot projects and studies have typically involved blending Hydrogen up to around 18-20% (approximately one-fifth by volume) with CNG for use as fuel in vehicles like buses. 4. Statement 4 is incorrect. The production of hydrogen and the infrastructure required for blending make H-CNG currently *more* expensive than conventional CNG. 5. Therefore, only statements 2 and 3 are correct.