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
Phantom Tooth Pain 
Select and explain. 
A. Persistent pain after RCT for ≥ 6-month, B. not attributed to RCT, C. due to upregulation of C-Fos gene, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: None