Which of the following is an end product described as a gas commonly produced during decomposition?

• A. Methane
• B. Water
• C. Ammonia
• D. Oxygen

Answer: (A)

Decomposition yields different end products depending on whether oxygen is present. In aerobic decay, carbon dioxide and water are produced. In anaerobic decay, methane is formed by methanogenic microbes and escapes as a gas. Water isn’t a gas at room conditions, and oxygen isn’t produced by decomposition. Ammonia can be released in some cases but isn’t the characteristic gaseous end product you’d describe for decomposition. Therefore, methane is the gas commonly produced during decomposition.