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.

Identifies methane as the major component of CNG (CH4) — a carbon-containing fuel whose combustion produces CO2.

A student can use the fact that methane contains carbon while hydrogen does not to infer that replacing some methane with hydrogen will lower carbon per unit of fuel burned, and then compare energy contents to estimate CO2 change.

Defines types of hydrogen (grey/blue/green) and notes that hydrogen production methods differ strongly in carbon intensity.

A student can combine this with the idea of blending hydrogen into CNG to realise that net CO2 emissions depend on how the hydrogen was produced (low‑carbon electrolysis vs. carbon‑intensive SMR).

States the general rule that the most effective way to reduce CO2 is to reduce fossil fuel consumption.

A student can treat hydrogen as a non‑fossil (or lower‑carbon) additive to CNG and infer that replacing fossil methane with hydrogen should reduce CO2 emissions per unit fossil fuel displaced.

Notes that fuel‑cell vehicles using hydrogen produce near‑zero pollution, with CO2 and water vapour being the only emissions in that context.

A student can use fuel‑cell hydrogen as an example of low‑CO2 hydrogen use, and contrast combustion of blended H‑CNG with pure hydrogen fuel‑cell pathways to judge potential CO2 benefits.

States that natural gas (CNG) is emerging as a transport fuel for vehicles and buses.

A student can combine this with methane’s role in CNG to frame a practical comparison of bus fuel options and calculate fleet‑level CO2 impacts if hydrogen is blended into existing CNG supplies.

Identifies CNG introduction as a step to reduce vehicular air pollution, implying CNG is a cleaner transport fuel compared with conventional fuels.

A student could infer that if CNG already lowers emissions, modifying its composition (by adding H2) might further change emission profiles and so should be tested for HC changes.

Lists use of alternate fuels such as CNG as an important measure to reduce vehicular emissions, establishing a baseline that fuel composition affects pollution.

Using the general rule that fuel type affects emissions, a student could reason that hydrogen enrichment could alter combustion chemistry and thus HC emissions, meriting measurement.

Explains methane (CH4) is the main component of CNG and notes its chemical composition (hydrogen atoms bound to carbon).

A student aware that adding free hydrogen (H2) changes the hydrogen-to-carbon ratio could predict combustion differences that might reduce unburnt hydrocarbons, and so would look for empirical HC measurements for H-CNG vs CNG.

States that fuel-cell vehicles (using hydrogen) produce near-zero pollution (CO2 and water vapor), highlighting that hydrogen combustion/oxidation produces mainly water.

A student can combine this with basic chemistry to hypothesize that increasing hydrogen fraction in a fuel could shift emissions toward more complete oxidation (less HC), suggesting experimental comparison of HC emissions.

Notes vehicle emission control measures (e.g., catalytic converters, good quality fuels, and CNG) which links emission outcomes to fuel quality and after-treatment.

A student could use this pattern to reason that both fuel composition (H-CNG) and emission controls determine HC output, so controlled tests comparing H-CNG and CNG with the same after-treatment are needed.