The system used by protozoa to help control the flow of water into the cell is:

A.	tugor pressure against the cell wall.
B.	a pump in the cytoplasm that squeezes out water. Yes, a membrane bound contractile vesicle collects water that enters the cell by osmosis. A microfilament contractile system squeezes the accumulated water back into the aqueous medium.
C.	the Na+ K+ ATPase of the cell membrane.
D.	the lysosome, used to secrete water in animal cells.