Which type of respiration does not require oxygen?

• A. Aerobic respiration
• B. Anaerobic respiration
• C. Fermentation
• D. Photosynthesis

Answer: (B)

In cellular energy production, the presence or absence of oxygen as the final electron acceptor in the electron transport chain distinguishes the pathways. When oxygen isn’t available, organisms can still generate ATP through anaerobic respiration, using other molecules such as nitrates or sulfates as the final electron acceptors. This keeps the electron transport chain functioning and produces ATP, though not as much as aerobic respiration. Fermentation also occurs without oxygen, but it bypasses the electron transport chain entirely, so it isn’t categorized as respiration in the same sense. Photosynthesis is a different process that builds sugars using light. Therefore, the type that does not require oxygen is anaerobic respiration.