Trick question: asexuals don't screw anything.
What's an asexual person's favorite thing to do in the bedroom?
How can you tell an asexual designed a street?
"The not enter signs at all intersections."
Okay, two that came up at school:
1) What do you call an asexual panromantic? A pan cake!
2) Someone walked into a room I was in and announced "The queen is here!"
My response? "Ace trumps queen".
It all honestly depends. There is a spectrum within asexuality, (and, really, any sexuality I suppose,) about how people feel about sex. The three common terms are sex-repulsed, sex-indifferent, and sex-favorable.