alleryDuring quiet inspiration, the diaphragm
Adomes upward into the thorax
Bflattens downward, increasing thoracic volume
Cstays still; only ribs move
Dmoves laterally outward
Answer & Solution
Correct answer: B. flattens downward, increasing thoracic volume
The diaphragm is a muscular dome.
Contraction flattens it, pulling downward, expanding the thoracic cavity
→ pressure drops → air flows in.
Relaxation domes it back up → air flows out.
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