Good Riddles

Question: A father's child. A mother's child. no one's son.

Who am I?

Question: If a pirate was to join the military, what branch of the armed service would they probably go in to?

Question: You have a flashlight that takes 2 working batteries. You have 8 batteries but only 4 of them work.

What is the fewest number of pairs you need to test to guarantee you can get the flashlight on?

Question: I have two rings. I move by request. If the mixture isn't right I just sit and rest.

What am I?

Question: I go up and I go down,
towards the sky and the ground.
I'm present and past tense too,
Let's go for a ride, me and you.

What am I?