I'd second what everyone said. I would suspect most cis-people have never once been asked about whether their genitals match their gender expression. Nor should you be asked that.
For a doctor, an intimate partner, with a therapist, or, perhaps, a *VERY* close friend, it may be appropriate (depending on how you feel - I'd still say that you shouldn't be required to disclose to anyone). But for everyone else, if you wouldn't go up to them and ask about their genitals, it's probably not a relationship where they should be doing that to you. You will get more respect from others if you obviously expect respect from them. And it just plain isn't respectful to ask about genitals in most situations.
You might be able to use it as a teachable moment to explain why you don't want to answer, if they are friends.
So my long post can be summarized: If you wouldn't ask them about their parts, they shouldn't ask about yours.