This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Electron Transport Chain and Biological Oxidation, Subject name: Biochemistry
P : O ratio for FAD is - 
Select and explain. 
A. 3, B. 2[?]5, C. 1[?]5, D. 4
C: 1[?]5
Answer: C: 1[?]5 
Explanation: Ans. is 'c' i.e., 1[?]5o The P : O ratio is a measure of the number of high energy phosphates (i.e., number of ATP molecules) synthesized per atom of oxygen consumed or per molecule of water is producedo The P : O ratio for oxidation of metabolites that yield NADH is 2[?]5 and the ratio for those that yield FADH2 is 1[?]5.