This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Trauma, Subject name: Surgery
[{'content': 'Chronic subdural haenatoma refers to collection present for a period of \nSelect and explain. \nA. 7 days, B. 6 months, C. 1 year, D. 21 days', 'role': 'user'}, {'content': 'Answer: D \nExplanation: REF; GREENBERG HANDBOOK OF NEUROSURGERY 8th edi, p-895', 'role': 'assistant'}]