Which gas is NOT a result of fossil fuel combustion?

The correct choice indicates that methane is not a direct result of fossil fuel combustion. When fossil fuels such as coal, oil, and natural gas are burned, they primarily produce gases like carbon dioxide, nitrogen oxides, and sulfur dioxide as byproducts. Carbon dioxide is a significant greenhouse gas and a direct output of fossil fuel combustion, as is nitrogen oxide, which contributes to air pollution and smog. Sulfur dioxide, released from the burning of fossil fuels containing sulfur, can lead to acid rain.

Methane, on the other hand, is typically produced during the extraction and transportation of fossil fuels or from natural sources such as wetlands and agricultural activities, rather than as a direct product of combustion. When fossil fuels are burned, methane is not produced in significant amounts; instead, it is often the fuel itself or a leakage issue that brings methane into discussions about greenhouse gases associated with fossil fuel use. This distinction is important in understanding the different environmental impacts associated with fossil fuel extraction and combustion.