This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head and neck, Subject name: Surgery
The most common cyst of the oral region is 
Select and explain. 
A. Dentigerous cyst, B. Keratosis cyst, C. Dermoid cyst, D. Periapical cyst
D: Periapical cyst
Answer: D: Periapical cyst 
Explanation: repeated question.