Answer:
I cost no money to use, or conscious effort to take part of. And as far as you can see, there is nothing to me. But without me, you are dead.
I have four legs but no tail. Usually I am heard only at night.
What is round as a dishpan, deep as a tub, and still the oceans couldn't fill it up?
What can burn the eyes, sting the mouth, yet be consumed?
What common English verb becomes its own past tense by rearranging its letters?
What did the piece of wood say when he saw the screwdriver and screws approaching?
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?