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
If a bur cuts a hole measurably larger than the head diameter, the defect is usually because of: 
Select and explain. 
A. Concentricity, B. Runout, C. Wornout blades, D. Altered taper angle
B: Runout
Answer: B: Runout 
Explanation: Runout is the more significant term clinically, because it is the primary cause of vibration during cutting and is the factor that determines the minimum diameter of the hole that may be prepared by a given bur. Burs normally cut holes measurably larger than the head diameter because of runout defects.