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
Retreatment file used for GP removal rotate at: 
Select and explain. 
A. 350 RPM, B. 900 RPM, C. 1200 RPM, D. 1500 RPM
D: 1500 RPM
Answer: D: 1500 RPM 
Explanation: "Optimum speed for GP removal with rotary instruments is about 1500rpm".