Which term describes the energy-releasing process that requires oxygen?

• A. Fermentation
• B. Photosynthesis
• C. Transpiration
• D. Respiration

Answer: (D)

Energy-releasing processes that use oxygen are about extracting energy from molecules by oxidizing them, with the main example being cellular respiration. In this process, glucose is broken down in mitochondria, and oxygen acts as the final electron acceptor in the electron transport chain. This flow of electrons drives the production of a large amount of ATP, the cell’s energy currency, while producing carbon dioxide and water as waste. Because respiration describes this oxygen-using way of getting energy from glucose, it’s the best term for the description. Fermentation also releases energy but does so without oxygen and yields much less ATP; photosynthesis stores energy using light rather than releasing it, and transpiration is simply water movement in plants.