During Strenuous Exercise, the NADH Formed in the Glyceraldehyde 3-Phosphate $\rightarrow$

During strenuous exercise, the NADH formed in the glyceraldehyde 3-phosphate dehydrogenase reaction in skeletal 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 $\rightarrow$ glycerol 3-phosphate.
B) glucose 6-phosphate $\rightarrow$ fructose 6-phosphate.
C) isocitrate $\rightarrow$ $\alpha$ -ketoglutarate.
D) oxaloacetate $\rightarrow$ malate.
E) pyruvate $\rightarrow$ lactate.