81. β-oxidation of fatty acids, which one of the following reactions is correct? (A) Two NADH are produced for each acetyl-CoA. (B) Oxidation of an 18-carbon fatty acid produces six molecules of propionyl-CoA. (C) Uses only even–chain, saturated fatty acids as substrates. (D) Uses NADP+ . (E) Occurs by a repeated sequence of four reactions.