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: Dental
[{'content': 'The width of bracket most commonly used are: \nSelect and explain. \nA. 0.017 and 0.021, B. 0.014 and 0.024, C. 0.018 and 0.028, D. 0.010 and 0.020', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]