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': 'All of the following are virulence factors of peussis, except: \nSelect and explain. \nA. Tracheal cytotoxin, B. Peussis toxin, C. Capsule, D. Peactin', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is. 'c' i. e., Capsule", 'role': 'assistant'}]