The correct answer is A. CH4.
CNG stands for compressed natural gas. It is a mixture of methane (CH4) and other hydrocarbons, such as ethane (C2H6) and propane (C3H8). CNG is a clean-burning fuel that produces fewer emissions than gasoline or diesel fuel. It is also a more efficient fuel, meaning that vehicles that use CNG get better gas mileage than those that use gasoline or diesel fuel.
B. CO2 is carbon dioxide, a greenhouse gas that contributes to climate change. C. N2 is nitrogen, an inert gas that does not contribute to pollution. D. H2 is hydrogen, a clean-burning fuel that is not currently used in automobiles on a large scale.
CNG is a good choice for reducing pollution because it is a clean-burning fuel that produces fewer emissions than gasoline or diesel fuel. It is also a more efficient fuel, meaning that vehicles that use CNG get better gas mileage than those that use gasoline or diesel fuel.