Animals which are unable to adjust their internal salt concentration according to the external environment are:

Explanation

"Osmoregulators" tightly regulate their body osmolarity, which always stays constant and is more common in the animal kingdom. "Osmoregulators" actively control salt concentrations despite the salt concentrations in the environment. The term "Thermoregulatory" is associated with temperature. "Osmoconformers" are organisms that keep their internal fluids isotonic to their environment. They maintain an internal salinity similar to their ambient conditions (e.g., most marine invertebrates and seagrass). "Anhydrobiosis" means 'life without water and refers to the remarkable ability of some organisms to survive the loss of all, or almost all, water and enter into a state of suspended animation in which their metabolism comes reversibly to a standstill. Therefore, D is the correct option.