All of the Following Are Animal Mechanisms to Cope with the Problem

All of the following are animal mechanisms to cope with the problem of water balance EXCEPT

A) coupling of water/salt removal with metabolic waste removal.
B) contractile vacuoles.
C) passage of water and waste of the body across a layer of cells into a tubular structure.
D) kidneys used as filtering organs.
E) secretion of regulatory hormones into the tubule.