Answer:
D.The diaphragm contracts and thoracic volume increases.
Step-by-step explanation:
During inhalation, the diaphragm and intercostal muscle contract which results in the expansion of the lungs. Due to this increase, the pressure is reduced. This decrease of pressure within the thoracic cavity as compared to the surroundings makes which creates a pressure gradient between the environment and the thoracic cavity. Due to the pressure gradient, air rush into the lungs