Unlike most bony fishes, sharks maintain body fluids that are isoosmotic to seawater, so they are considered by many to be osmoconformers. Nonetheless, these sharks osmoregulate at least partially by
A) monitoring dehydration at the cellular level with special gated aquaporins.
B) using their gills and kidneys to rid themselves of sea salts.
C) possessing a special adaptation that allows their cells to operate at an extraordinarily high salt concentration.
D) tolerating high urea concentrations that balance internal salt concentrations to seawater osmolarity.
E) synthesizing trimethylamine oxide, a chemical that binds and precipitates salts inside cells.
Answer: D