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
According to Ellis and Davey classification a fracture of 51 involving dentin and associated loss of vitality is classified as 
Select and explain. 
A. Class 2, B. Class 4, C. Class 8, D. Class 9
D: Class 9
Answer: D: Class 9 
Explanation: None