The correct option is A osmoconformers
In the aquatic environment, the osmotic balance of organisms is determined by the osmotic concentration of the surrounding water. Marine organisms such as jellyfish, mussels, crabs, lobsters and starfish maintain an osmotic balance similar to that of the surrounding seawater, and are known as osmoconformers.
Osmoregulators on the other hand are organisms that maintain an internal osmotic balance.
Homeotherms, also called endotherms are organisms that regulate their body temperature.
Poikilotherms on the other hand do not regulate their body temperature and the temperature of the organism varies along with the ambient temperature.