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
Patients with Down's syndrome normally have: 
Select and explain. 
A. IQ score above 80, B. Brachycephalic skull, C. Stiff muscles, D. All of the above
B: Brachycephalic skull
Answer: B: Brachycephalic skull 
Explanation: None