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': "Down's syndrome is associated with all of the following\nexcept \nSelect and explain. \nA. Retrognathia, B. Periodontal disease, C. Premature exfoliation of teeth, D. Retained deciduous teeth", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]