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
Dentin Protection during cavity restoration is most
important when the "remaining dentin thickness" is: 
Select and explain. 
A. 1 — 2mm, B. 1.5 mm, C. 0.5 — 1mm, D. 0.5 mm
D: 0.5 mm
Answer: D: 0.5 mm 
Explanation: None