Which of the following is listed as an output of the Electron Transport Chain?

• A. 4 CO2
• B. 10 NADH, 2 FAD
• C. Oxygen accepts electrons to form water
• D. 10 NAD+, 2 FAD, 32-34 ATP

Answer: (C)

The electron transport chain’s defining output is water formed when oxygen acts as the final electron acceptor. As electrons flow through the chain, oxygen accepts them along with protons to become H2O, which is the direct product of this stage. The other items reflect inputs to the chain (NADH and FADH2) or outputs from earlier stages (CO2 from the TCA cycle) or the broader energy yield tied to ATP synthesis, which depends on the proton gradient rather than being a direct product of the chain itself. So, oxygen accepting electrons to form water best describes what the chain directly produces.