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 hard carious dentin is removed with \nSelect and explain. \nA. Excavator, B. Bur at Low speed, C. Bur at high speed, D. None of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]