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 dye used in the "Reductase enzyme" (caries activity\ntest) is \nSelect and explain. \nA. Diazoeresorcinol, B. Bromocresol green, C. 1% acid red in propylene glycol, D. Methyl blue', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]