The __________ of the instrument is a clue to its specific use

Which of the following statements BEST describes the exchange of gas in the alveoli?

A) Air moves into the alveoli, blood is transported by the pulmonary capillaries, and diffusion occurs. B) Blood moves by way of the pulmonary capillaries, air arrives at the alveoli, and osmosis occurs. C) Air moves into the airway, blood arrives via the pulmonary veins, and osmosis occurs. D) Blood moves from the left heart to the lungs, air arrives in the alveoli sacks, and diffusion occurs.

The elastic nature of the arteries allows them to _____ during systole and _____ during diastole to maintain vascular pressure

A. relax, contract B. contract, relax