Question: There're two people in front of you: your friend and an imposter looking exactly like your friend. There's no way to determine who is who by asking questions, they know the same information about you. You have only one bullet in your gun. If you kill or injure the imposter, you and your friend will be saved, If you're wrong, he'll kill you immediately. How will you know?
Answer: Ask them to drop their weapon, the one who won't obey is the imposter.
Question: I am the first son of my father, I can live without men but men can't live without me, the second son of my father has seen men rise and fall and have all of their secrets in his belly, the third son of my father can never give you his gift forever, he takes it from you when you corrupt it unknowingly but men cry for his gift no matter its cost, the fourth son of my father is an obedient servant in the hands of men but when he losses his master he becomes an unmercifully god, the fifth son of my father is the center of our lives, he guides us but he is a divine mystery. What are we?
Answer: Water, earth, air, fire and spirit.