How to deal with mean, nosey girls?

In my cles this year, I have to sit with a couple of those sneaky, bully girls that pick on people that can't or are too afraid to say anything back. When it comes to being mean, these girls are top notch. They made fun of the special needs kids in the hallway on our first day coming to cl. And I don't need to know what to say to them if they're out right rude to me, because I'll let them have it. But what is the best way to deal with those nosey questions that girls like that ask. I mean, they'll ask you how many guys you dated/kissed/slept with/etc. and not really care what the answer is, they just want something to make fun of you for, or to gossip about. They ask these questions like they're just curious, or are just being friendly, too, so its hard to go off the handle and tell them to mind their own business, because they made it sound like they were genuinely curious. So what is the best way to answer a question like that without lying? Something that I can say to avoid those "how many have you slept with* questions?