This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology, Subject name: Microbiology
[{'content': 'Most sensitive test for HIV infection - \nSelect and explain. \nA. Western blot, B. PCR, C. Agglutination test, D. CFT', 'role': 'user'}, {'content': 'Answer: B \nExplanation: repeat', 'role': 'assistant'}]