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': 'For cutting dentin by Gates Glidden drills, it should be used at: \nSelect and explain. \nA. 200-300 rpm, B. 450-800 rpm, C. 750-1000 rpm, D. None of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: It is\xa0ideally\xa0used to cut dentin\xa0as it is withdrawn from the canal.\xa0\nIt cuts on the outstroke, and it is used to open canal oriﬁce.\xa0\nIt is used in 750-1000 rpm.\nLong shaft is designed so as to break at the neck, the narrowest diameter that lies adjacent to the handpiece.\xa0\nIf the drill binds during use, it will fracture at the neck of the shaft.', 'role': 'assistant'}]