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: Pathology
The pathogenesis of periapical cyst is? 
Select and explain. 
A. Increased pressure within the cyst, B. Immune mediated bone destruction, C. Proliferation of epithelium, D. None
C: Proliferation of epithelium
Answer: C: Proliferation of epithelium 
Explanation: None