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': 'Common spinal cord tumor with intradural but extramedullary situation -a)  Meningiomab)  Neurofibromac)  Ependymomad) Astrocytoma \nSelect and explain. \nA. ab, B. a, C. ad, D. bc', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]