This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Protozoa, Subject name: Microbiology
Largest protozoan is? 
Select and explain. 
A. E. Histolytica, B. Balantidium coli, C. E.coli, D. Plasmodium
B: Balantidium coli
Answer: B: Balantidium coli 
Explanation: ANSWER: (B) Balantidium coliREF: Jawett's 24th edition Section VI. Parasitology > Chapter 46-Medical Parasitology"Balantidium coli, the cause of balantidiasis or balantidial dysentery, is the largest intestinal protozoan of humans"