The what is located in the center of the u. s. and part of southern canada?

The answer is    d.  central highlands

It has to be understood that the sea water contains a huge amount of sodium and chlorine ions and if they enter the cell of the atlantic cod fish, the cell will shrivel and the fish will die. to avoid such a condition, the fish uses active transport for the purpose of removing the ions against the gradient. i hope it you.