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': 'Percentage of distal root with two root canals in mandibular molar \nSelect and explain. \nA. 10%, B. 30%, C. 60%, D. 1%', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]