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 second number in a four number instrument formula denotes \nSelect and explain. \nA. Blade angle, B. Blade length, C. Primary cutting edge angle, D. Blade width', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]