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': "Yard-stick of detection in Snyder's test is: \nSelect and explain. \nA. Acid formation, B. pH change, C. Count of microorganisms, D. Enamel solubility", 'role': 'user'}, {'content': 'Answer: B \nExplanation: Snyder\'s test uses\xa0Bromocresol\xa0green as an indicator, which is blue-green at pH 5.4 or above and turns yellow at pH 3.8 or less.\xa0\nThe "critical pH" for enamel dissolution is 5.4-5.5.\nTherefore, it would be more appropriate to use an indicator such as\xa0Bromocresol purple, which is purple at pH 6.8 and yellow at pH 5.2.\n\nSoben Peter 5th edition\nPage number\xa0 434', 'role': 'assistant'}]