Saltwater fish constantly drink water but still excrete concentrated urine to compensate for the water loss. They also have gills to help excrete excess salts. Conversely, freshwater fish absorb salt from their surroundings using their gills and their bodies reabsorb salt from their urine. This describes how salt- and freshwater fish _______.

Saltwater fish lose water to their salty surroundings, so they drink and produce concentrated urine while removing excess salt through their gills. Freshwater fish face the opposite problem and conserve salt while taking it up through their gills. These different ways of balancing water and salts are adaptations to osmosis, so the correct choice is “have adapted to deal with osmosis.”

AI-written and checked against the verified answer.