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 enamel has no capacity of self —repair because 
Select and explain. 
A. It has only a small percent of organic content, B. Its formative cells are lost once it is completely formed, C. It is essentially a keratin tissue and has no blood vessels, D. It has no direct connection with the active cells of the dental pulp
B: Its formative cells are lost once it is completely formed
Answer: B: Its formative cells are lost once it is completely formed 
Explanation: None