Question

according to the passage, a species is deemed aquatic if it has the function of:
living chiefly in water during its adult life.
keeping its skin wet at all times, even when walking on land.
developing gills and not lungs.

Explanation:

To determine the correct option, we analyze the definition of an aquatic species. An aquatic species is typically defined as one that lives mainly in water, especially during its adult life. The second option about keeping skin wet at all times is not a defining characteristic of aquatic species (many terrestrial species with moist skin aren't aquatic). The third option is incorrect as some aquatic species (like amphibians in adult stage) can have lungs and still be aquatic, and not all aquatic species rely solely on gills (e.g., some aquatic mammals). So the first option matches the typical definition of an aquatic species.

Answer:

A. living chiefly in water during its adult life.