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: Surgery
Causes of chronic constipation are all except: 
Select and explain. 
A. Hirschsprung disease, B. Chagas disease, C. Hypokalemia, D. Polyps
D: Polyps
Answer: D: Polyps 
Explanation: None