40. It is crucial that regulation occur at pyruvate dehydrogenase because: (A) pyruvate kinase is reversible (B) lactate dehydrogenase is the only other enzyme to use pyruvate (C) the product acetyl-CoA is committed to oxidation in the citric acid cycle or fatty acid biosynthesis (D) alanine aminotransferase would use the pyruvate (E) all of the above