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: Medicine
[{'content': 'In an AIDS patient presenting with a fever cough, a diagnosis of pneumocystis carinii pneumonia is best established by- \nSelect and explain. \nA. Transtracheal biopsy, B. Broncho alveolar lavage, C. Staining of intranuclear inclusion and silver staining, D. Aspiration and culture', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]