Which of the following statements best explains why NADH generates more energy than FADH2  when  it goes through the electron transport chain?

• A. NADH generates more energy because it carries more electrons than FADH₂.
• B. NADH generates more energy because it has a higher affinity for the electron transport chain proteins than FADH₂.
• C. NADH generates more energy because it directly contributes more protons to the proton gradient used for ATP synthesis than FADH₂.
• D. NADH generates more energy than FADH₂ because it donates its electrons at a higher energy level in the electron transport chain.

Answer: (D)