The correct option is D Both A and B
Biogas is a flammable gas that is produced from the fermentation or degradation of biomass in biogas plants. Biogas typically refers to a gas produced by the biological breakdown (degradation) of organic matter in the absence of oxygen. whereas the breakdown of organic matter, usually by bacterial action, resulting in the formation of other substances of less complex constitution with the evolution of ammonia is known as putrification.