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?

Lists use of CNG as an alternate fuel to reduce vehicular emissions as a general pollution-control step.

A student could combine this with basic combustion knowledge to investigate which specific pollutants (e.g., CO, NOx, SPM) CNG typically reduces compared with diesel.

States that introduction of CNG in cities is a step to reduce transport emissions, implying CNG changes emission profiles from conventional fuels.

One could compare emission profiles of CNG-powered buses versus diesel buses to see whether CO elimination is the principal benefit or one among several.

Mentions measures (catalytic converters, fuel quality, use of CNG) that target specific pollutants like NOx and general vehicular pollution.

Use the list to frame which pollutants are commonly targeted and then check whether H‑enrichment primarily affects CO relative to these other pollutants.

Explains that methane (major component of CNG) is a simple hydrocarbon (CH4), establishing CNG's carbon-containing nature.

With basic combustion chemistry (outside knowledge), a student can reason that adding hydrogen (no carbon) changes fuel carbon content per unit energy and thus may affect CO formation.

Notes that fuel-cell vehicles emit near-zero pollution, with CO2 and water vapor being the only emissions, illustrating that hydrogen-based technologies can greatly alter pollutant outputs.

A student could contrast fuel-cell (pure H2) outcomes with H‑enriched CNG to judge whether adding H to a carbon fuel approaches elimination of carbon-containing emissions like CO.