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': 'D2 on the endodontic file indicates: \nSelect and explain. \nA. Diameter at tip of instrument, B. Angle of instrument, C. Length of instrument, D. 1/100th mm at end of cutting blade', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]