Contraction of the diaphragm decreases the volume inside of the ribcage, resulting in exhalation.

• A. True
• B. False
• C. Not determinable
• D. It increases volume

Answer: (B)

The main idea is how the diaphragm movement changes chest volume and drives breathing. When the diaphragm contracts, it moves downward and flattens, increasing the volume of the thoracic cavity. This rise in volume lowers the pressure inside the lungs, so air flows in—inhale. Exhalation happens mainly when the diaphragm relaxes, allowing the chest to recoil and the thoracic volume to decrease, which increases intrapulmonary pressure and pushes air out. So the statement is false: contraction does not decrease volume or cause exhalation; it increases volume and promotes inhalation.