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
Amount of gap required for cement in restoration is: 
Select and explain. 
A. 10-25 microns, B. 2 microns, C. 50-100 microns, D. No gap required
A: 10-25 microns
Answer: A: 10-25 microns 
Explanation: None