Respiration begins when air enters the mouth and nose. As air goes down the trachea, or windpipe, tiny hairs called cilia gently wave to keep dirt and mucus out. At the bottom of the trachea are two tubes called bronchi. One bronchus goes into the left lung, and the other goes into the right lung. When you inhale, the diaphragm muscle between the lungs and abdomen contracts, making room for the lungs to expand. Which of these best describes how the lungs and diaphragm affect each other?

A
As the lungs expand, the diaphragm expands.

B
As the lungs expand, the diaphragm contracts.

C
As the lungs contract, the diaphragm contracts.

D
The lungs and diaphragm have no relationship.