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: Pharmacology
Derivative of morphine used for diarrhea is: 
Select and explain. 
A. Oxymorphine, B. Diphenoxylate, C. Pethidine, D. Codeine
B: Diphenoxylate
Answer: B: Diphenoxylate 
Explanation: None