Imagine an Invertebrate That Lives in an Estuary Where Salinity

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) slight fluctuations that are kept within a narrow range.
B) regular variations that range from large to small.
C) a cyclic variation opposite that of the surrounding water.
D) a cyclic variation depending upon when the animal drinks.