7. In glycolysis, the NADH formed in the glyceraldehyde 3-phosphate dehydrogenase reaction in vigorously contracting muscle must be reoxidized to NAD+ if glycolysis is to continue. The most important reaction involved in the reoxidation of NADH is: (A) dihydroxyacetone phosphate=＞ glycerol 3-phosphate. (B) pyruvate=＞lactate. (C) glucose 6-phosphate=＞ fructose 6-phosphate. (D) isocitrate=＞α-ketoglutarate. (E) oxaloacetate=＞malate.