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': 'What percent of cases with injury to kidney require surgical exploration - \nSelect and explain. \nA. 20%, B. 90%, C. 50%, D. 70%', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is \'a\' i.e., 20% "Surgical exploration is needed in less than 10 percent of closed injuries and is indicated if either there a signs of progressive blood loss or there is an expanding mass in the loin."- Bailey 25/e', 'role': 'assistant'}]