Anaerobic bacteria may use ________ as the final electron acceptor during anaerobic respiration.

• A. oxygen (O_2)
• B. glucose (C_6H_{12}O_6)
• C. carbon dioxide (CO_2)
• D. nitrate (NO_3^-)

Answer: (D)

Verified step by step guidance

1. Understand that in anaerobic respiration, bacteria use a molecule other than oxygen as the final electron acceptor in their electron transport chain.
2. Recall that oxygen (O_2) is the final electron acceptor in aerobic respiration, so it is not used in anaerobic respiration.
3. Recognize that glucose (C_6H_{12}O_6) is a substrate (electron donor) rather than an electron acceptor.
4. Identify common alternative electron acceptors used by anaerobic bacteria, such as nitrate (NO_3^-), sulfate (SO_4^{2-}), or carbon dioxide (CO_2).
5. Conclude that nitrate (NO_3^-) is a typical final electron acceptor in anaerobic respiration, making it the correct choice.