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 number of bacteria in the oral cavity is greater \nSelect and explain. \nA. in the morning, B. after meals, C. at night, D. after brushing', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]