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 diameter of the tip of a periodontal probe is: 
Select and explain. 
A. 0.25 mm, B. 0.75 mm, C. 0.5 mm, D. 1 mm
C: 0.5 mm
Answer: C: 0.5 mm 
Explanation: None