Which of the following is NOT an end product of decomposition?

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

Answer: (C)

When organic matter decomposes, microbes break it down into simpler, more stable molecules. In aerobic conditions, this process uses oxygen and ends up primarily as carbon dioxide and water. Some decomposition pathways release ammonia from nitrogen-containing compounds, and in environments without oxygen, methane can be produced. Oxygen, however, is not generated as a product of decomposition; it is typically consumed during the process. That’s why oxygen is not an end product, while ammonia, water, and methane can be end products under different conditions.