Refer to the Figure Below

Refer to the figure below. NAD⁺ functions as a coenzyme in many enzyme-catalyzed reactions.The changes that take place in this coenzyme are the same for all of these reactions and are illustrated in the figure.It is likely that, in these reactions, NAD⁺

A) functions as an electron donor in an oxidation-reduction reaction.
B) functions as an electron acceptor in an oxidation-reduction reaction.
C) forms a covalent intermediate during covalent catalysis.
D) induces strain in other substrates bound at active sites.
E) functions as a base in acid-base catalytic mechanisms.