This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Central Nervous system, Subject name: Pharmacology
[{'content': 'Which of the following is not an opioid peptide? \nSelect and explain. \nA. Beta Endorphin, B. Epinephrine, C. Leu5-encephalin, D. Met5-encephalin', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Beta endorphin, leu-5 encephalin, met-5encephalin are all opiod peptides. Ref KD Tripathi 8th ed.', 'role': 'assistant'}]