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': 'Occlusal caries index (ICDAS 1 and Histological Validation), code 4 means? \nSelect and explain. \nA. Enamel demineralization Limited to outer 50% of enamel, B. Demineralization involving inner 50% of enamel upto DEJ, C. Demineralization involving outer 50% of dentine, D. Demineralization involving inner 50% of dentine', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]