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': 'Which of the following is not a feature of extramedullary tumour? \nSelect and explain. \nA. Early Coicospinal signs and paralysis, B. Root pain or midline Back -pain, C. Abnormal CSF, D. Sacral sparing', 'role': 'user'}, {'content': "Answer: D \nExplanation: Sacral sparing is a feature of intramedullary tumors, not extra medullary tumors. So sacral sparing is the single best answer of choice. Ref: Harrison's Principles of Internal Medicine, 16th Edition, Page 2440", 'role': 'assistant'}]