Which statement about the citric acid cycle is correct? a) the last reaction in the citric acid cycle produces a product that is a substrate for the first reaction of the citric acid cycle. b) the citric acid cycle oxidizes glucose to carbon dioxide. c) the oxidation of compounds by the citric acid cycle requires molecular oxygen. d) the citric acid cycle depends on the availability of nad+, which is a product of glycolysis. e) the citric acid cycle produces most of the atp that is subsequently used by the electron transport chain.