The correct answer is C. Methane.
Marsh gas is a flammable gas that is found in swamps and marshes. It is composed mostly of methane, which is a colorless, odorless gas that is lighter than air. Marsh gas is formed when organic matter decomposes in the absence of oxygen. This can happen in swamps, marshes, and other areas where there is a lot of water and little oxygen.
Marsh gas can be dangerous if it is not properly ventilated. It can cause explosions and fires if it comes into contact with a spark or flame. It can also be harmful to human health if it is inhaled.
Nitrogen is a colorless, odorless gas that makes up about 78% of the Earth’s atmosphere. It is not flammable and does not support combustion.
Ethane is a colorless, flammable gas that is found in natural gas and petroleum. It is used as a fuel and as a chemical feedstock.
Hydrogen is a colorless, odorless, and tasteless gas that is the lightest element in the universe. It is flammable and supports combustion.