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
All of the following influence the efficiency of bur, except: 
Select and explain. 
A. Neck diameter, B. Length and diameter of bur, C. Height of taper of bur, D. Spiral angle and cross-cuts of bur
C: Height of taper of bur
Answer: C: Height of taper of bur 
Explanation: None