You are in a dungeon and there are two doors in front of you. One door leads to certain death, the other leads to freedom. You must pick one of the doors but you don't know which door is which.
Guarding the doors, there are two people in the room. One of them always tells the truth, but one of them always lies. You must ask one of them a single question but you don’t know which person always lies and which person doesn’t.
What question should you ask in order to determine which door leads to freedom?