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: Pediatrics
[{'content': 'Commonest cause of obstructive hydrocephalus in children – \nSelect and explain. \nA. Acqueductal stenosis, B. Aqueductal gliosis, C. Subarachnoid hemorrhage, D. Tubercular meningitis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]