In its purest form, what is CNG composed of?

CNG, or compressed natural gas, is primarily composed of methane (CH4). Methane is the simplest alkane and the main component of natural gas, making it the focus for CNG. When natural gas is processed, predominantly methane is compressed to form CNG, which is used as a fuel alternative due to its clean-burning properties.

The other options—propane, butane, and ethane—are also hydrocarbons found in natural gas but are not the primary component of CNG. While propane and butane can serve as fuels and may be mixed with natural gas, they are heavier and differ in characteristics like storage and combustion performance. Ethane, while a component of some natural gas mixtures, is also not the main constituent of CNG. Thus, methane stands out as the correct choice for the composition of CNG.