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: Surgery
[{'content': 'Chronic subdural haematoma 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: None', 'role': 'assistant'}]