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': 'Electronic apex locator is used in Endodontics to determine the \nSelect and explain. \nA. Root canal morphology, B. Working length, C. Pulp stone Location, D. Pulp vitality', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]