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': 'Most commonly used local anesthesia \nSelect and explain. \nA. 1:20,000 xylocaine Hcl, B. 1:50,000 xylocaine Hcl, C. 1:10,000 xylocaine Hcl, D. 1:80,000 xylocaine Hcl', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]