A Riddle
You are trapped in a room with two men. One of them always lies, the other always tells the truth, but you do not know which is which. There are two doors leading from the room. One of the doors leads to instant and certain death. The other door leads to safety and freedom. The two men in the room with you both know which door is which (apparently you're not the first one in this predicament), but only you are allowed to choose which door to open.
What is the fewest number of questions you can ask in order to ascertain which door to open? You may ask either man any question you'd like, but each time counts as a single question. If you ask both men the same question, that is still two questions.