As a result of glycolysis, pyruvate oxidation and the citric acid cycle, only a small portion of the energy of glucose has been converted to ATP. At this point, the majority of the usable energy is contained in:

A.	oxidized electron carriers NAD+ and FAD
B.	carbon dioxide
C.	pyruvate
D.	acetyl coenzyme A
E.	reduced electron carriers NADH and FADH