Animals That Move Between Salt and Fresh Water Are Able

Animals that move between salt and fresh water are able to survive large fluctuations of external osmolarity because they are

A) able to alter the water permeability of their skin, gills and guts.
B) able to tolerate large fluctuations in cell volume.
C) able to change from being osmoconformers in salt water to being osmoregulators in fresh water.
D) able to regulate their extracellular fluid by retaining higher concentrations of urea.
E) osmoregulators that are able to switch from a strategy that conserves water in the marine environment to one that sheds excess water in the freshwater environment.