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': "All of the following about Down's syndrome are true except: \nSelect and explain. \nA. PDL degeneration takes place, B. Tooth never exfoliates though there is advanced PDL loss, C. Deep periodontal pockets associated with a substantial plaque, D. Acute necrotizing lesions are a frequent finding", 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]