Ammonia Is Toxic and Must Be Secreted as a Dilute

Ammonia is toxic and must be secreted as a dilute solution.Why do most freshwater fish secrete ammonia,but mammals do not?

A) Freshwater fish do not have enough energy to convert ammonia to ureA.
B) Mammals do not break proteins down forming ammonia.
C) Mammals do not secrete wastes in solution.
D) Freshwater fish can release ammonia without becoming dehydrated by drinking water.
E) Mammals can synthesize urea from ammonia without using energy.