Why do boys mess with girls that don't like them?

They would usually mess with girls that don't like them because...

a) They like the girl and are trying to hint that to them, but boys aren't very good flirters so you will have to try and guess or...

b) They are obnoxious twirps and are full of themselves so are trying to get the prettiest girlfriend they can, just to show off.

Hope this helps =]