Puzzle Please help me to solve this

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you are in a room and the room has two door. each door has a guard. you have to go out of the room but out of one door there is life and out of the other door its death waiting for you. more to it, one guard always speaks truth and other guard always tell a lie. but you dont know which guard speaks truth and which guard is a liar and which one is life door and which one is death door but the guard sitting knows where is life and where is death. now what you have to do , you have to ask a question from any one guard about the door from where if you go out you survive. so please help me and tell me what would be your question hint; question should be so descriptive that you identify the life door.