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': 'The term TUG BACK is used to indicate \nSelect and explain. \nA. Good fit of accessory gutta-percha point at the apical third, B. Good fit of master gutta-percha point at the apical third, C. Good fit of accessory cone in the main body of the canal, D. Good fit of the initial file at the apical third', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]