Good Riddles

Question: I can be dropped from the tallest of buildings and survive,but drop me from the smallest ship and I won't.What am I?

Question: When you're given one, you'll have either two or none?

Question: You can only keep it once you give it to somebody.

What is it?

Question: A vivid reality, a naked morality, a place where wishes come true.

Question: It takes ten men ten hours to build a certain wall. How long does it take five men to build the same wall?