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': 'Which of the following drugs is most frequently used in treating refractory periodontitis, including localized juvenile periodontitis? \nSelect and explain. \nA. Metronidazole and Amoxicillin, B. Tetracycline, C. Ciprofloxacin, D. Penicillin', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]