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': 'In the Dentocult lactobacilli test, low caries activity is determined by: \nSelect and explain. \nA. ＞10,000 C.F.U, B. ＜1000 C.F.U, C. ＜1,000,000 C.F.U, D. ＜10,000 C.F.U', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]