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 thickness of cement-dentinal junction? 
Select and explain. 
A. 1-2 μm, B. 2-3 μm, C. 3-4 μm, D. 4-5 μm
B: 2-3 μm
Answer: B: 2-3 μm 
Explanation: None