The correct answer is A. Oxygen.
Oxygen is a gas that is essential for combustion, or burning. When oxygen combines with other elements, it releases energy in the form of heat and light. This is why fire needs oxygen to burn.
Carbon monoxide is a gas that is produced when carbon is burned in an incomplete combustion process. It is a poisonous gas that can cause death
if inhaled.Nitrogen is a gas that makes up about 78% of the Earth’s atmosphere. It is not flammable and does not support combustion.
Carbon dioxide
is a gas that is produced when carbon is burned in a complete combustion process. It is not flammable and does not support combustion.In conclusion, oxygen is the only gas that helps in burning.