A lab observation notes that freshwater protozoans repeatedly collect and expel excess water from the cell. The observation points to:

The contractile vacuole removes excess water entering a freshwater protozoan by osmosis. Without this structure, the cell could swell and burst in hypotonic surroundings. This MCQ belongs to the Protozoan osmoregulation topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.