How does the structure of the alveoli allow for its function of gas exchange?
a. alveolar sacs produce 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.

On the bahamian island of andros, mosquitofish populations live in isolated freshwater ponds that were once united. currently, some predator-rich ponds have mosquitofish that can swim in short, fast bursts; predator-poor ponds have mosquitofish that can swim continuously for a long time. when placed together in the same body of water, the two kinds of female mosquitofish exhibit exclusive breeding preferences. if one builds a canal linking a predator-rich pond to a predator-poor pond, then what type(s) of selection should subsequently be most expected among the mosquitofish in the original predator-rich pond, and what type(s) should be most expected among the mosquitofish in the original predator-poor pond?