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': 'Retreatment file used for GP removal rotate at: \nSelect and explain. \nA. 350 RPM, B. 900 RPM, C. 1200 RPM, D. 1500 RPM', 'role': 'user'}, {'content': 'Answer: D \nExplanation: "Optimum speed for GP removal with rotary instruments is about 1500rpm".', 'role': 'assistant'}]