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: Anaesthesia
[{'content': 'All are opioid agonist - antagonist compounds except – a) Buprenorphineb) Nalbuphinec) Pentazocined) Nalmefenee) Papaverine \nSelect and explain. \nA. ab, B. bc, C. cd, D. de', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Agonist antagonist opioids Pentazocine, Nalbuphine, Nalorphine, Butorphanol, Levallorphan, Dezocine, Meptazinol, Buprenorphine.', 'role': 'assistant'}]