The Lady or the Tiger?

The King built a public arena where men accused of a crime must choose one of two doors. Behind one of the doors is a lady; behind the other is a tiger. If the prisoner chooses the door with the tiger, he is assumed to be guilty, and he will be eaten in front of the entire kingdom. On the other hand, if he chooses the door with the lady, he is presumed innocent, and he marries the lady right there on the spot.