How does the structure of the alveoli allow for its function of gas exchange?
A
Alveolar sacs have space to hold mucus that makes gas exchange easier.B
Alveolar sacs rely on valves to ensure that air flows only in one direction.C
Alveolar sacs are located within muscles that contract, which increases gas exchange.D
Alveolar sacs are surrounded by thin capillaries where gases can be exchanged.