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
[{'content': 'Most of the cases of Listeria are due to serovar ? \nSelect and explain. \nA. 2, B. 4a, C. 4b, D. 6', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is `c' i.e., 4b", 'role': 'assistant'}]