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
Apexification is the treatment of choice for a permanent tooth with wide open apex when: 
Select and explain. 
A. The pulp is necrotic, B. The pulp is vital, C. The pulp and root canals are calcified, D. There is traumatic pulp exposure during cavity preparation
A: The pulp is necrotic
Answer: A: The pulp is necrotic 
Explanation: Apexification is the process of inducing the development of the root and the apical closure in an immature pulpless tooth with an open apex.
The main aim of apexification is to preserve the Hertwig’s root sheath and apical pulp tissue.

Ref :Textbook of endodontics, Nisha Garg and Amit Garg, 3rd edition, pg no:548