脑筋急转弯:what question can never be answered by "yes"?

You can never answer this question with "Yes":

Are you asleep?

http://www.cybermacedonia.com/jokes.html

你睡觉时
我也做过

Do you never say "yes"?

你死了吗？

Are you asleep?(你睡着了吗?)

Are you sleep?