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': 'The thickness of prismless enamel in deciduous teeth is: \nSelect and explain. \nA. 25 μm, B. 50 μm, C. 75 μm, D. 100 μm', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A relatively structureless or prismless layer of enamel, approximately 30μm thick is present in 70% of permanent teeth and all deciduous teeth.', 'role': 'assistant'}]