The correct answer is b: Coenzyme A.
During the process of pyruvate oxidation, acetyl CoA molecule is produced. Pyruvate oxidation is the link between glycolysis and Krebs cycle and it converts pyruvate (three-carbon molecule) into acetyl-CoA ( two-carbon molecule attached to Coenzyme A). NADH is produced and one CO2 released. AcetylCoA is the substrate for the next stage of cellular respiration, citric acid cycle.