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 number on the handle of a root canal instrument denotes \nSelect and explain. \nA. Length of the instrument in 1/10 of a millimetre, B. Length of the instrument in millimetres, C. Diameter at the tip in 1/100 of a millimetre, D. Diameter at the tip in 1/10 of a millimeter', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]