This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Parasitology Pa 1 (Protozoology), Subject name: Microbiology
[{'content': 'All are true about Balantidium coli except: \nSelect and explain. \nA. It is a protozoa, B. Cyst is the infective stage, C. Usually invades liver, D. It is the largest protozoan parasite inhabiting large intestine in man', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Balantidium coli Only ciliate protozoa and the largest causing human disease (ciliate dysentery). Infective stage: binucleate cyst; spherical, ellipsoid, 50-75mm, double layered cyst wall. The invasive form is the trophozoite - 80-120mm; two nuclei (macronucleus, micronucleus), peristome, cytostome, cytopharynx, cytopyge.', 'role': 'assistant'}]