The correct answer is: contractile vacuoles.
Paramecium is simple unicellular ciliate that lives in the water environments. It is often used as model organism in laboratory experiments because of its ability to easy conjugate and divide.
Osmoregulation of the paramecium is regulated by contractile vacuoles (one or more within the cell). Contractile vacuoles expel water from the cell in order to compensate for fluid absorbed by osmosis from its water surroundings.