Which of these is a primary component of CNG?

Methane is the primary component of compressed natural gas (CNG). It is a colorless and odorless gas that consists primarily of carbon and hydrogen, making it a hydrocarbon. CNG is primarily used as a cleaner alternative to gasoline or diesel for powering vehicles and operates primarily because of its high-energy content and lower emissions when combusted.

The other options do not serve as primary components of CNG. Propane and butane, while also hydrocarbons, are different types of fuels commonly classified as liquefied petroleum gases (LPG), which are distinct from CNG. Oxygen, on the other hand, is not a hydrocarbon and is involved in the combustion process rather than being a component of natural gas itself. Overall, methane's role as the main constituent is critical to understanding the properties and functionality of CNG.