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: Pathology
[{'content': 'Positive zone of enamel caries is the: \nSelect and explain. \nA. Translucent zone, B. Dark zone, C. Body of the lesion, D. Surface zone', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The dark zone\nThis lies adjacent and superficial to the translucent zone. It has been referred to as the ‘positive zone’\xa0because it is usually present. This zone is formed as a result of demineralization and appears dark brown in ground sections examined by transmitted light after imbibition with quinolone.', 'role': 'assistant'}]