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: Radiology
Most common epicenter of a radicular cyst is: 
Select and explain. 
A. Distal surface of tooth, B. Apex of tooth involved, C. Mesial surface of tooth, D. Deep periodontal pocket
B: Apex of tooth involved
Answer: B: Apex of tooth involved 
Explanation: In most cases, the epicenter of a radicular cyst is located approximately at the apex of a nonvital tooth. It occasionally appears on the mesial or distal surface of a tooth root at the opening of an accessory canal or infrequently in a deep periodontal pocket. 
Oral radiology White and Pharaoh; 7th ed. Page no 335