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': 'In CPR the sternum should be depressed at a rate of \nSelect and explain. \nA. 1 inch per 1 second, B. 2 inch per 1 second, C. 1 inch per 5 second, D. 2 inch per 5 second', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]