Answer:
Acclimatization
Explanation:
Acclimatization is the change in the body of an organism in response to changes in the environment to maintain equilibrium (homeostasis). In the case of the salmon, when the environment changes from fresh to salt water and back, the chemical homeostasis would be altered if the fish didn't adjust. The adjustments in the fish gills are the response of the fish to acclimatize to the changes in the chemical environment in order to maintain homeostasis.
I think its A
A dog will bark at animals and cars, but only if the environment permits.
-Seth
Vein because they have valves to prevent back flow of blood.