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
Which of the following methods is not an acceptable way to determine instrument sharpness? 
Select and explain. 
A. Evaluation of the cutting edge during scaling procedures, B. Evaluation of light reflection from the cutting edge when observed under magnification, C. Evaluation of the cutting edge against plastic testing stick, D. Evaluation of the cutting edge against the clinicians finger nail
D: Evaluation of the cutting edge against the clinicians finger nail
Answer: D: Evaluation of the cutting edge against the clinicians finger nail 
Explanation: None