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
Mineral trioxide aggregate used in apexification: 
Select and explain. 
A. Forms an integral part of the root canal filling, B. Dissolves as the apical barrier formation progresses, C. Has not yielded good results, D. Is available in a paste form
A: Forms an integral part of the root canal filling
Answer: A: Forms an integral part of the root canal filling 
Explanation: None