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 zinc in ZOE cement is: \nSelect and explain. \nA. 60%, B. 70%, C. 80%, D. 90%', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]