Final answer:
The diaphragm's movement is crucial for breathing; it contracts and moves downward during inhalation to enlarge the thoracic cavity, creating a vacuum that draws air into the lungs.
Step-by-step explanation:
When you move the diaphragm, it enables breathing by changing the volume of the thoracic cavity. During inhalation, the diaphragm contracts and moves downward, creating a partial vacuum in the thoracic cavity into which outside air flows. As a result, the chest volume gets larger and the lungs take in air. The control of breathing is regulated by the brain stem, which sends nerve impulses to the diaphragm via the autonomic nervous system, monitoring the level of carbon dioxide in the blood to maintain homeostasis of blood gases and pH.
In the context of the provided options, the correct answer to what happens when you move the diaphragm is:
d. It creates a partial vacuum in the thoracic cavity into which outside air flows during inhalation.