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': 'Gracey curettes have a characteristic feature that \nSelect and explain. \nA. They are used for area of surface of the tooth, B. They have double cutting edge, C. They can be used any where in oral cavity, D. All', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]