Answer:
What is the only question you can't answer yes to?
How do you discover something that does not exist?
An archaeologist unearths a coin bearing the inscription "57BC". How does he instantly know that it's a forgery?
What is the largest $ amount of change you can have in your pocket without having exact change for $1?
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?
Black we are and much admired. Many seek us if they are tired. We tire the horse, and comfort man, and turn White when we've fulfilled your plan.