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: Medicine
Which of the following is not seen in Prader Willi syndrome. 
Select and explain. 
A. Mental retardation, B. Short stature, C. Hypotonia, D. Inappropriate laughter
D: Inappropriate laughter
Answer: D: Inappropriate laughter 
Explanation: Inappropriate laughter is a feature of Angelman syndrome.