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': 'Renal trauma is best treated by \nSelect and explain. \nA. Observation and supportive measures, B. Early drainage of perirenal haematoma, C. Heminephrectomy, D. Nephrostomy', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]