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': 'Infrabony pocket results from \nSelect and explain. \nA. Trauma from occlusion, B. Dental plaque, C. Actinomyces viscosus, D. Improper tooth brushing', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]