Best riddles for teens

I go around all the places, cities, towns and villages, but never come inside. What am I?

What did the boy bird say to the girl bird on Valentine's Day?

What do you throw out when you want to use it, but take in when you don't want to use it?

What type of cheese is made backwards?

We hurt without moving. We poison without touching. We bear the truth and the lies. We are not to be judged by our size. What are we?

What has six faces, but does not wear makeup. It also has twenty-one eyes, but cannot see?

What is the center of Gravity?

You see a boat filled with people. It has not sunk, but when you look again you don't see a single person on the boat. Why?

As small as your thumb, I am light in the air. You may hear me before you see me, but trust that I'm there. What am I?

What is the similarity between a tooth and a tree?