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
In general, hand sharpening of instruments with
unmounted stones is preferable to sharpening by motor - driven mounted stones because unmouted stones 
Select and explain. 
A. have a finer grain, B. are less likely to alter the bevel, C. are easier to sterilize, D. wear away less of the instrument surface
D: wear away less of the instrument surface
Answer: D: wear away less of the instrument surface 
Explanation: None