Answer:
What can be as big as an elephant but weighs nothing?
As a state in America I am round on both sides and high in the middle.
I help engines spin and pants stay up.
I dig out tiny caves and store gold and silver in them. I also build bridges of silver and make crowns of gold. Sooner or later everybody needs my help yet many people are afraid to let me help them.
I take off my clothes when you put on your clothes. I put on my clothes when you take off your clothes. What am I?
When is it bad luck to see a black cat?