What Am I Riddles

Question: What is often picked but seldom chosen, never walks but can run when frozen?

Question: Swallowing one is fine.
Swallowing two together is fine.
But Swallow them separately and all shall fall.

What are they?

Question: I'm small but big, i hide behind you but come out when you fall... What am I?

Question:

Look at my apple, keep me near.

Listen closely, I'll put worms in your ear.

What am I?

Question: I'm measured in temperature and time, but have neither.

What am I?