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
MTA barrier in open apex is made up to? 
Select and explain. 
A. 3mm, B. 5mm, C. Depend on length of canal, D. 1mm
B: 5mm
Answer: B: 5mm 
Explanation: None