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
Root canal treated tooth are hard to resorb because of 
Select and explain. 
A. Lack of vitality of pulp results in loss of neuropeptides, B. Cementum becomes more calcified, C. Lack of differentiation of odontoclast because of no live cells, D. PDL become necrosed
A: Lack of vitality of pulp results in loss of neuropeptides
Answer: A: Lack of vitality of pulp results in loss of neuropeptides 
Explanation: None