Good Riddles

Question: A man builds a rectangular house. After he builds the house he wants to place a clock on a south wall. Because there are so many south walls he places the clock on a random wall. He sits in front of the sits in front of the clock for ten minutes until he hears a knock on his font door. The man opens the door to see a bear on his front porch. The bear kills him. What color was the bear and why?

Question: What is the only question you can never answer?

Question: What is it that you have that no one else has?

Question: What number is odd but then when i get one letter from it turns into EVEN

Question: im fast and slow I go everywhere you go yet you cannot see me im in tree's in the sky in plants and in your body pretty much you need me to survive what am I?