This is such a loaded question. I PERSONALLY believe that if a chick is asking you this question PRIOR to sleeping with you, it probably means that SHE is pretty selective and and is not your standard hor that 80+% of western woman are. If in this situation I would simply ask "why does it matter?", and her body language will tell you what you should say next regardless of what comes out of her mouth. Notice how drunk chicks and ONS never ask you this question? Because they are hors and don't give a sh1t, they are LOW quality.
But, this is just my personal opinion, yours will varys, and no one has the end all be all answer to this question.