Answer:
When is homework not homework?
How do you discover something that does not exist?
What moves and touches water but doesn't get wet?
A girl is sitting in a house at night that has no lights on at all. There is no lamp, no candle, nothing. Yet she is reading. How?
I have two coins, one is marked George I and one is marked George IV. One is genuine but one is a forgery. Which is the forgery?
It is something you will never see again.