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 childern, most common posterior fossa tumour is- \nSelect and explain. \nA. Meningioms, B. Astrocytoma, C. Medulloblastoma, D. Glioblastoma multiforme', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]