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
The second number in a four number instrument formula denotes 
Select and explain. 
A. Blade angle, B. Blade length, C. Primary cutting edge angle, D. Blade width
C: Primary cutting edge angle
Answer: C: Primary cutting edge angle 
Explanation: None