Answer:
What can you throw but not catch?
What is it that no man ever yet did see, which never was, but always is to be?
Who has married many women but never has been married who is he
What type of paper can you neither read nor write on?
Always old, sometimes new. Never sad, sometimes blue. Never empty, sometimes full. Never pushes, always pulls.
Black we are and much admired. Many seek us if they are tired. We tire the horse, and comfort man, and turn White when we've fulfilled your plan.