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': 'Depth of demineralization for dentin is: \nSelect and explain. \nA. 10 micron, B. 7.5 micron, C. 6 micron, D. 20 micron', 'role': 'user'}, {'content': 'Answer: B \nExplanation: In enamel, the resin tags are approximately 6 µm in diameter and 10 to 20 µm in length and lead to micromechanical interlocking.\nPhillips 12th edition page 260\nDentin is demineralized by up to approximately 7.5 µm depending on the type of acid, application time, and concentration.\n\nSturdevant 7th edition page 144', 'role': 'assistant'}]