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': 'Among the following, the structure that is most calcified is \nSelect and explain. \nA. Enamel lamella, B. Enamel rod, C. Enamel spindle, D. Enamel tuft', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]