Question

how would the contractile vacuole of a freshwater amoeba respond if the organism was placed in seawater?
with more contractions
with fewer contractions
the contractions would suddenly cease
with the same frequency of contractions

Explanation:

A freshwater amoeba's contractile vacuole expels excess water that enters the cell by osmosis (since freshwater is hypotonic to the amoeba's cytoplasm). When placed in seawater (which is hypertonic to the amoeba's cytoplasm), water will move out of the amoeba. So, there is less excess water for the contractile vacuole to pump out.

Answer:

with fewer contractions