When you exhale, or breathe out, the process happens in reverse. The diaphragm, which had contracted and moved down, now relaxes and moves back up. The ribs contract, creating a smaller space in the chest. After the body has used the oxygen it needs, the blood carries carbon dioxide and other waste products. Blood comes back to the capillaries, and the waste products enter the alveoli. Then they are breathed out through the bronchioles, bronchi, trachea and finally the nose and mouth. What happens to the rib cage when you exhale?

A
It expands.

B
It disappears.

C
It gets smaller.

D
It stays the same.