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: Physiology
Following are gastrointestinal hormones except 
Select and explain. 
A. CCK, B. GIP, C. Motilin, D. Chymotrypsin
D: Chymotrypsin
Answer: D: Chymotrypsin 
Explanation: Chymotrypsin is an enzyme. Others are all hormones.