Contraction of the diaphragm allows air inside (diaphragm moves down).

• A. False
• B. Decreases air intake
• C. True
• D. Not sure

Answer: (C)

Breathing relies on the diaphragm changing the volume of the chest cavity. When the diaphragm contracts, it moves downward and flattens, expanding the thoracic cavity. This increase in volume lowers the pressure inside the lungs relative to the outside air, so air is drawn into the lungs. That’s why the statement “Contraction of the diaphragm allows air inside (diaphragm moves down)” is true. If the diaphragm didn’t contract, air wouldn’t be pulled in; the opposite would be the case during exhalation when the diaphragm relaxes and air is pushed out. The option implying decreased air intake or uncertainty doesn’t fit with how breathing works.