Answer:
What is the building that you leave without ever having entered.
How can you throw a ball 20 meters, and have it come back to you without hitting anything?
You draw a line. Without touching it, how do you make the line longer?
A claustrophobic person gets on a train. The train enters a tunnel just as it is leaving the station. Where is the best place for him to sit?
A girl is sitting in a house at night that has no lights on at all. There is no lamp, no candle, nothing. Yet she is reading. How?
What is it that makes tears without sorrow. And takes its journey to heaven?