Question

select an option below that describes what you observe.
hide hint
hint: remember we are looking for observations of the characteristics of life.
paramecium use contractile vacuoles to pump water out of the cell, because living in water results in water coming in across their cell membrane. the contractile vacuoles help them keep the correct concentration of water in the cells.
the contractile vacuoles are producing new cells.
the contractile vacuoles stay the same size, but the cell grows.
the beating of the cilia on the outside is keeping the inside of the cell the same.
the contractile vacuoles are pumping every once and a while, but the cell stays the same size.

Explanation:

Paramecia are aquatic protists that take in water via osmosis, so their contractile vacuoles regularly pump excess water out to maintain cell size and internal water balance, which is an observable characteristic of their life function. The other options are incorrect: cilia are for movement, not internal balance; contractile vacuoles do not produce cells; and the vacuoles do not stay the same size as they fill and empty while the cell maintains size.

Answer:

The contractile vacuoles are pumping every once and a while, but the cell stays the same size.