Answer:
Contraction of diaphragm causes the greatest change in thoracic volume during quiet inspiration.
Explanation:
Quiet respiration is an active process involving :
1) Contraction (Descent) of diaphragm : It results in increase in the vertical diameter causing the greatest change in thoracic volume.
2) Elevation of ribs (External intercostal) : It results in an increase in anterposterior and lateral diameter
