Which statement provides the best evidence that the muscular system interacts with the respiratory system to carry out life processes?

A. The absorption of oxygen by sacs called alveoli shows how specialized tissues are necessary for movement of substances through the respiratory system.

B. The initiation of the breathing process by the phrenic nerves shows how neurons are necessary for blood oxygenation.

C. The protection provided by the rib bones shows how the respiratory system needs hardened organs to keep it working properly.

D. The diaphragm’s movement downward to draw air into the lungs shows how muscles are necessary to bring air into the body.