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': 'Periodontal tissue destruction apically and potentially migrating towards the gingival margin is called \nSelect and explain. \nA. Marginal periodontitis, B. Marginal Gingivitis, C. Retrograde Periodontitis, D. chronic destructive periodontitis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]