One of the ways through which freshwater fish compensate the loss of salts from their bodies is that they

Explanation

The correct answer is that freshwater fish uptake salts by gills and skin via active transport (Option C). Freshwater fish live in an environment where the concentration of salts is lower than in their bodies, causing them to lose salts. To counteract this, they actively absorb salts from the water through their gills and skin.Option A is incorrect because drinking large amounts of water would exacerbate the problem of dilution. Option B is incorrect because freshwater fish produce a large volume of dilute urine to get rid of excess water, not concentrated urine. Option D is incorrect as retaining urea is not a strategy used by freshwater fish; it is more relevant to marine organisms.