This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
[{'content': 'Undulant fever is caused by \nSelect and explain. \nA. Salmonella typhi, B. Staphylococcus aureus, C. Brucella melitensis, D. Coxiella burnetti', 'role': 'user'}, {'content': "Answer: C \nExplanation: Acute brucellosis is mostly due to B.melitensis. It is usually known as undulent fever, but this is misleading as only some cases show the undulent pattern. It is associated with prolonged bacteremia and irregular fever. Ref: Textbook of microbiology; Ananthanarayan and paniker's; 10th edition; Pg:347", 'role': 'assistant'}]