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
What is the optimum depth for a pinhole in a tooth with a vital pulp 
Select and explain. 
A. 4-5 mm, B. 2-3 mm, C. 2 mm, D. 1-1.5 mm
C: 2 mm
Answer: C: 2 mm 
Explanation: None