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
Down's syndrome is associated with all of the following
except 
Select and explain. 
A. Retrognathia, B. Periodontal disease, C. Premature exfoliation of teeth, D. Retained deciduous teeth
A: Retrognathia
Answer: A: Retrognathia 
Explanation: None