16. During intense physical activity, NADH generated in glycolysis is rapidly reoxidized by which reaction? (A) Reduction of pyruvate to lactate by lactate dehydrogenase. (B) Conversion of glucose-6-phosphate to fructose-6-phosphate. (C) Oxidation of dihydroxyacetone phosphate to glycerol-3-phosphate. (D) Reduction of oxaloacetate to malate. (E) Formation of citrate from oxaloacetate and acetyl-CoA.