Best riddles with simple answers

I have more than 80 keys, but I cannot open any lock. What Am I?

I dig out tiny caves, and store gold and silver in them. I also build bridges of silver and make crowns of gold. They are the smallest you could imagine. Sooner or later everybody needs my help, yet many people are afraid to let me help them. What am I?

What is the largest ant in the world?

What can you hold without ever touching it?

There is bomb on top of a computer; around the computer are a hairbrush, keys, phone and a cup. When the explosion comes, what item destroyed first?

Can you write number 45 using only the number 4?

What clothes does a house wear?

Only one color, but not one size. Stuck at the bottom, yet I easily fly. Present in sun, but not in rain. Doing no harm, and feeling no pain. What Am I?

What can you swallow than can also swallow you?

What goes up and down the stairs without moving?