In terms of neurotransmitter activity, how does the mechanism of erection differ from that of orgasm?

a. Erection depends on acetylcholine, and orgasm depends on serotonin.

b. Erection depends on increased dopamine release, and orgasm depends on decreased dopamine release.

c. Erection depends on one set of dopamine receptors, and orgasm depends on different dopamine receptors.

d. Erection depends on serotonin, and orgasm depends on nitric oxide.