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': 'Best laboratory test to diagnose HIV infection March 2007 \nSelect and explain. \nA. ELISA, B. Western blot, C. Complement fixation test, D. RIA', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B: Western blot', 'role': 'assistant'}]