Answer:
Tuesday, Sam and Peter went to a restaurant. After eating lunch, they paid the bill. Sam and Peter did not pay. Who did?
I am needed for most animals and hardcover books
In many hall ways you would stand if not with me in hand.
The more you work the more I'll eat.You keep me full I'll keep you neat.
I can be in your body but never on your placemat. I'm always better when I'm fresh, but you'll never see me in the flesh. What am I?
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.