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': 'Specific gravity of enamel is: \nSelect and explain. \nA. 2.1, B. 2.8, C. 3.2, D. 3.4', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]