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 lactobacillus count test to assess caries activity was given by: \nSelect and explain. \nA. Snyder, B. Jay, C. Hadley, D. Edelstein', 'role': 'user'}, {'content': 'Answer: C \nExplanation: LACTOBACILLUS COLONY COUNT TEST\n\nThis caries activity test was introduced by Hadley in 1933.\n\nEssentials of preventive and community dentistry\xa0\nSoben Peter\xa0\n5th edition', 'role': 'assistant'}]