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
Diameter of medium Bristles tooth brush should be: 
Select and explain. 
A. 0.1mm., B. 0.2mm., C. 0.3mm., D. 0.4mm.
C: 0.3mm.
Answer: C: 0.3mm. 
Explanation: Diameter of medium Bristles tooth brush is 0.3mm or 0.012 inch.