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
The thickness of the alginate impression material between the tray and the tissues should be at least 
Select and explain. 
A. 1mm, B. 2mm, C. 3mm, D. 5mm
C: 3mm
Answer: C: 3mm 
Explanation: None