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 following affects prognosis of periodontal treatment 
Select and explain. 
A. Short root, long crown, B. Long root, short crown, C. Apical pearls, D. Root concavities
D: Root concavities
Answer: D: Root concavities 
Explanation: None