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': 'Undulant fever is caused by - \nSelect and explain. \nA. Baonella, B. Brucella melitensis, C. Bordetella, D. Borelia recurrentis', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Brucella melitensis . Acute brucellosis also known as undulant fever is mostly due to Br. melitensis.", 'role': 'assistant'}]