A) MOST definitely bottom, I do not use bum, arse or ass at all and tend to find these are a male trait now there's a little insight for you, now you can tell when you are on websites or exchanging E mails with someone that they are male if they use these words as a terminology for a bottom. Females as a rule don't like any part of the anatomy referred to in a vulgar way, yes we all know it appeals to males but women are far less course. I also like posterior or derriere when referring to a bottom.