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': 'Which of the following is used for Rickettsia ? \nSelect and explain. \nA. Weil-Felix reaction, B. Rose-waler test, C. Poul-Bunnel test, D. VDRL', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Weil-Felix reaction", 'role': 'assistant'}]