You are trapped in a room with two doors. You know there is a pack of hungry lions, certain death, past one door, and freedom behind the other. There are also two people, one guarding each door. They both know which door has freedom. One always tells the truth, the other always lies. You don't know who is who. You ask the person guarding door 1 one question. Then you need to choose a door. What question do you ask to give you a 100% chance of survival?