Which of the following is the largest protozoan?

Balantidium coli is a unicellular protozoan parasite with a length up to 200 micrometer, making it the largest of the human intestinal protozoa. It belongs to the Ciliophora phylum and is the only protozoan ciliate to infect humans. It goes through two development phases: a cyst and a trophozoite. Balantidiasis is often asymptomatic. The trophozoites invade the mucosa and submucosa of the large intestine and destroy the host cells when multiplying. Clinical symptoms are similar to amoebiasis.