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': 'Pneumocystis carinii is diagnosed by - \nSelect and explain. \nA. Sputum examination for trophozoites and cyst under microscope, B. Culture, C. Positive serology, D. Growth on artificial media', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]