1. No comment.
2. I'm not at liberty to say. (= I don't have permission to give the information)
3. Wait and see. (= you will discover the answer later)
4. Let me get back to you. (= I will give you the answer later)
5. I'm sorry, that's confidential.
6. I'm sorry, that's personal.
7. I'd rather not talk about it.
8. It's none of your business.
9. Mind your own business.
10. Why do you want to know?
#8 and #9 are rather rude – telling the other person to stop inquiring about your life

Fact
The rapid rate of expansion of gas is what gives steam its power. One volume of water, at normal atmospheric pressure and at the boiling point, yields 1,670 volume of steam.      .. More >>