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: Dental
[{'content': 'Apicoectomy is indicated in which one of the following cases? \nSelect and explain. \nA. Persistent positive results of root canal culture for microorganisms, B. Incomplete obturation in apical part of root canal with persistent infection, C. Fracture of apical one-third area of root in a vital asymptomatic tooth, D. Presence of a minor pulp stone in pulp chamber', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]