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': 'Recommended observation period prior to orthodontic treatment in minor Periodontal injuries: \nSelect and explain. \nA. 3 months, B. 6 months, C. 9 months, D. 12 months', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Recommended observation periods prior to orthodontic treatment', 'role': 'assistant'}]