Final answer:
Freshwater organisms have osmoregulatory mechanisms to survive in their hypotonic environment. They take ions up through gills or skin and produce dilute urine. Therefore, animals in freshwater are hyposmotic regulators.
Step-by-step explanation:
Freshwater organisms have evolved osmoregulatory mechanisms to survive in their hypotonic environment. They tend to take in water passively due to the hypotonicity of the environment, resulting in the production of dilute urine. They also actively transport salts through their gills to maintain electrolyte balance. Therefore, option c is the correct answer as animals in freshwater take ions up through gills or skin.