In one turn of the citric acid (Krebs) cycle per acetyl-CoA (excluding ATP from oxidative phosphorylation), what is the direct energy yield in terms of reduced cofactors and substrate-level phosphorylation?

• A. $3NADH$, $1FAD{H}_2$, and $1GTP$ (or ATP equivalent)
• B. $1NADH$, $1FAD{H}_2$, and $3ATP$
• C. $4NADH$, $1FAD{H}_2$, and $2GTP$
• D. $2NADH$, $2FAD{H}_2$, and $1ATP$

Answer: (A)