Answer:
Sorry @Josh2013, the answer is B. heart beating.
Explanation:
The reason for this answer is heart beating is an involuntary action, it happens on it's own. Eating, sleeping, and crying are all voluntary actions. And a behavior is an action you do voluntarily.
The real world examples that I can give is the everyday
things that we do and some of these are:
I am walking to the end of the room holding three textbooks.
Playing tug of war with friends.
Getting the groceries from the car and put it inside of your house.