The correct answer is:
A) lots of fresh water flowing across the gills of a fish.
Nitrogenous wastes, formed by the breakdown of proteins and nucleic acids (both contain nitrogen in their structure) tend to form toxic ammonia. Since it is toxic and raises the pH of body fluids it requires ATP and large quantities of fresh water to dilute it out of a biological system. So, only aquatic animals tend to release ammonia into the water (terrestrial animals release urea or ureic acid). Animals that excrete ammonia are said to be ammonotelic.
