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 ideal tooth - blade working angulation of a Blade of Gracey curette is angled from lower shank approximately at 
Select and explain. 
A. 10 - 20 degree, B. 40 - 50 degree, C. 60 - 70 degree, D. 80 - 90 degree
C: 60 - 70 degree
Answer: C: 60 - 70 degree 
Explanation: None