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: Surgery
On radiograph of upper lateral incisor a periapical lesion is found after 2 years following RCT curretage was done and histopathology showed presence of apical cyst. Lesion continued to enlarge even after surgery, What is the reason for this. 
Select and explain. 
A. Leaking from main canal, B. Unobturated accessory canal, C. Apex was not resected, D. Actinomycoses infection
A: Leaking from main canal
Answer: A: Leaking from main canal 
Explanation: None