What is the primary component of natural gas?

The primary component of natural gas is methane, making it the correct choice. Methane is a simple hydrocarbon with the chemical formula CH4 and constitutes about 70-90% of natural gas. It is colorless, odorless, and highly combustible, which makes it a valuable fuel source for heating, electricity generation, and as a raw material in various chemical processes.

In contrast, the other substances listed, such as ethanol, propane, and butane, are either not the primary components of natural gas or are used in different applications. Ethanol is an alcohol and is not associated with natural gas but rather with biofuels. Propane and butane are also hydrocarbons but are normally found in liquefied petroleum gas (LPG), not natural gas. While they can be present in small quantities in natural gas, they do not make up the majority of its composition. Thus, methane's dominance in the composition of natural gas confirms it as the correct answer.