This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Which of the following organism is biggest ? 
Select and explain. 
A. Balantidium coli, B. Entamoeba coli, C. Escherichia coli, D. Entamoeba histolytica
A: Balantidium coli
Answer: A: Balantidium coli 
Explanation: Ans. is 'a' i.e., Balantidium coli