In mitochondrial oxidative phosphorylation, what are the direct products of the electron transport chain (ETC) reactions (excluding ATP synthesis by ATP synthase)?

• A. A proton electrochemical gradient across the inner mitochondrial membrane and water (from reduction of $O_2$)
• B. Reduced coenzyme Q (ubiquinol) and cytosolic NADH
• C. $C{O}_2$ and $F{A}_{D_2}$
• D. Acetyl-CoA and a proton gradient across the outer mitochondrial membrane

Answer: (A)