Answer:
Osmoregulation
Explanation:
Contractile vacuoles are the membrane bound organelle present in the certain protists. These vacuoles serve in osmoregulation. The freshwater protists have hypertonic cells as compared to their surroundings, water enters into their cells through osmosis. The contractile vacuoles take in the water and expel it to prevent the bursting of protist's cells due to intake of excess water.
