At a Work Christmas Party, John (23) Got Drunk and Hit

At a work Christmas party, John (23) got drunk and hit on his boss's daughter, Alexis. They slept together, but John regretted it the next morning, realizing that he didn't find her attractive after all. Alexis told her father that they were dating, and now John is looking for a new job to get out of this relationship. He has to stay with her until he lands a new job, but he's having trouble getting an erection when they're in bed together. His friend advises him to just pop Viagra and soldier on. Will that help?

A) Viagra enables blood flow to the penis but only when a man is subjectively aroused, so it won't work if Alexis doesn't turn John on.
B) Viagra enables blood flow to the penis that causes an instant physiological erection independent of the mood, so John can use it to feign arousal.
C) Viagra enables blood flow to the penis that causes an instant physiological erection, but after about 20 minutes subjective arousal is necessary to sustain it, so John would have to be quick with Alexis.
D) It is irrelevant because no doctor would prescribe Viagra to a healthy male in his twenties, and it's impossible to obtain the drug in any other way than through a prescription.