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
Which of the following is totally sterile: 
Select and explain. 
A. Periapical cyst., B. Periapical granuloma., C. Radicular cyst., D. None
B: Periapical granuloma.
Answer: B: Periapical granuloma. 
Explanation: None