What is the centre of gravity?

Why do people go to bed?

What kind of tree can you carry in your hand?

What's the only room from which no one can enter or leave

Buy me, smell me or deliver me, I do not change.

Who am I?

In one of the popular batman series movie "Batman Forever", there was a riddle that goes like "Tear me off and then scratch my head and I was red then and now I am back. Who am I?

How many words can a pen with half refill write?

A sea diver is a real show-off. He showed everyone that he can hold his breath underwater for 15 minutes.

I went to the diver and told him that I can be underwater for double the time i.e 30 minutes.
He responded that he will give me 100$ if I would be able to do it. I won 100$.

What did I do?

If 24H in a D => 24 hours in a day.
What does "64S on CB" stand for?

It's a protector.
It sits on a bridge.
One individual can see directly through it, while others wonder what it hides.

What is it?