d. lives in fresh water
Work Step by Step
Protists that live in fresh water need contractile vacuoles to pump water out of them. The contractile vacuole usually contains water, releasing water into the cell if needed; however, if there is too much water already inside the cell, the contractile vacuole will release water to the outside environment. If a protist cell contains too much water, it will burst, so the contractile vacuole has the important function of keeping water at an equilibrium level inside the protist.