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 sixth complication of diabetes mellitus is \nSelect and explain. \nA. Retinopathy, B. Rental failure, C. Ischemic heart diseases, D. Periodontitis', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]