Good Riddles

Question: What can one not keep, two hold, and three destroy?

Question: You have a glass of water that looks about half full. How can you tell, only using the glass of water itself, if the glass is half full or not?

The glass is a right cylinder.

Question: Imagine you are swimming in the ocean and a bunch of hungry sharks surround you. How do you get out alive?

Question: How many seconds are in a year?

Question: What is one in every doll, in every doll, in every doll?