Organisms employ a variety of evolutionary adaptations to help them maintain the chemical composition of body fluids. Which of the following is NOT an example of how a given organism maintains such a balance?
(a) Some marine invertebrates are osmoconformers; their body fluids are isosmotic with the surrounding environment.
(b)Many marine vertebrates offset osmosis by drinking large amounts of water and releasing salt through their gills.
(c) Freshwater fish counteract osmosis by drinking large amounts of water and limiting their urination and feeding.
(d)Terrestrial organisms reduce water loss with adaptations such as skin, waxy exoskeletons, and closable stomata.

Freshwater fish have blood that is saltier than the water they swim in. They have to save salt and excrete lots of water. So they have to excrete low salt urine but high in water volume, because lots of water enters the blood and gills by osmosis. Remember that water moves by osmosis to hypertonic environments.

Option A is true because if the organisms are isotonic the water net movement is 0.

Option B is true, fish use active transport to excrete salts through their gills.

Option D. Skin and waxy exoskeleton prevent water loss. Plants close stomata to prevent water loss.