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: Pathology
[{'content': "X-bodies called Birbeck granules are characteristically seen in - \nSelect and explain. \nA. Granulomatous vasculitis, B. Pulmonary alveolar proteinosis, C. Langerhan's cells granulomatosis, D. Idiopathic pulmonary alveolar proteinosis", 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]