The correct answer is C. Methane.
Methane is the main component of biogas, making up about 50-75% of the gas. It is a colorless, odorless, and flammable gas that is lighter than air. Methane is a good fuel because it burns cleanly and produces little pollution. It is also a renewable resource, as it can be produced from organic waste such as manure, sewage, and food scraps.
Butane and propane are also flammable gases, but they are heavier than air and can accumulate in low-lying areas, posing a risk of explosion. Ethane is a non-flammable gas that is used in the production of plastics and other chemicals.
Biogas is a renewable energy source that can be used to generate electricity, heat, and power vehicles. It is a clean and efficient fuel that can help reduce greenhouse gas emissions.