Answer: B) Methane Explanation: The main constituent of biogas is methane (55-70%), CO2 (30-45%) and some traces of gases such as H2S and ammonia. Biogas is produced under anaerobic conditions; the process is denominated as anaerobic digestion.

An autotroph is an organism that can produce its own food using light, water, carbon dioxide, or other chemicals. Because autotrophs produce their own food, they are sometimes called producers. Most autotrophs use a process called photosynthesis to make their food.