Answer:
The air sacs absorb more oxygen during vigorous exercise.
Step-by-step explanation:
Function of respiratory system is to carry out gaseous exchange to makes the blood rich in oxygen. Musculoskeletal system is involved in movement of body and needs oxygenated blood to drive the muscle contraction and body movements. Musculoskeletal system needs increased oxygen supply during vigorous physical activity to support the movement which in turn is fulfilled by increased absorption of oxygen by air sacs.