At Present,there Are No Osmotic Conformers in Any Freshwater Animal

At present,there are no osmotic conformers in any freshwater animal species on Earth.Why?

A) Marine animals have been in existence much longer than freshwater animals,and evolution of osmotic conformity has not occurred in freshwater animals yet.
B) Osmotic conformers must expend a great deal of energy,and evolution favors adaptations that conserve energy.
C) Marine environments are much more abundant on Earth than freshwater environments,allowing for more diversity of animal forms.
D) Fresh water has an osmolarity of 0,and no animal could survive with such a low plasma osmolarity.
E) Both a and b