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': 'True about endemic typhus \nSelect and explain. \nA. Man is the only reservoir of infection, B. Flea is a vector of disease, C. A rash developing into an eschar is characteristics of the disease, D. Culture is diagnostic', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]