Imagine an invertebrate that lives in an estuary where salinity varies cyclically with the tides. If this individual is able to adjust the salt concentration of its body fluids, its salt concentration will have:. a. a cyclic variation depending upon when the animal drinks. b. regular variations that range from large to small. c. slight fluctuations that are kept within a narrow range. d. a cyclic variation opposite that of the surrounding water.

Option C.

slight fluctuations that are kept within a narrow range.

Explanation:

An invertebrate that lives in an estuary where salinity varies cyclically with the tides. If this individual is able to adjust the salt concentration of its body fluids, its salt concentration will have slight fluctuations that are kept within a narrow range so has to maintain homeostasis and prevent the cells of the the invertebrate from not shrinking which can be due to the salt solution (Hypertonic).

Estuary is an area of water or shorelines where river meet the ocean. It normal do have concentration of salts. Organisms that live in estuaries must be able to adapt to their dynamic environments, wich is due to variations in water chemistry includes salinity, as well as physical changes like the rise and fall of tides.