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': 'The most potent analgesic agent is: \nSelect and explain. \nA. Fentanyl, B. Sufentanil, C. Remifentanil, D. Allentanil', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Sulfentanil is 5 times more potent than Fentanyl.Alfentanil and remifentanil are faster acting and recovery is rapid. Above three drugs are congeners of Fentanyl. Ref: KD Tripathi 8th ed.', 'role': 'assistant'}]