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: Pathology
Critical pH for initiation of caries in dentin is: 
Select and explain. 
A. 4.3-4.5, B. 5.2-5.5, C. 4.9-5.1, D. 6.2-6.5
D: 6.2-6.5
Answer: D: 6.2-6.5 
Explanation: Critical pH for initiation of caries in dentin is 6.2-6.5.
In addition, the critical pH for dentin is higher than for enamel, so demineralization is likely to start even before the pH reaches the critical level for enamel (pH = 5.5).