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 first number in the instrument formula indicates \nSelect and explain. \nA. Length of the blade in centimeters, B. 1/10th of the width, C. angulation of the blade in degrees, D. primary cutting edge angle', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]