This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Opioids and Alcohols, Subject name: Pharmacology
[{'content': 'Arrange the following opioids according to their potency (most potent first) a. Fentanyl b. Sufentanil c. Morphine d. Pethidine \nSelect and explain. \nA. a,d,c,b, B. b,a,c,d, C. a,d,b,c, D. b,c,d,a', 'role': 'user'}, {'content': 'Answer: B \nExplanation: a. Fentanyl group of opioids are most potent opioids. Among these most potent is Sufentanil (approx 1000 times more potent than morphine) . The sequence of potency from high to low in this group is Sufentanil > Fentanyl > Alfentanil. b. Pethidine is 10 times less potent than morphine', 'role': 'assistant'}]