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 patients shows: \nSelect and explain. \nA. Early exfoliation of deciduous teeth, B. Microdontia of teeth over retained teeth, C. Periodontitis, D. All of the above", 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]