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': 'Opioid antagonist that can be given orally – \nSelect and explain. \nA. Naltrexone, B. Naloxone, C. Nalbuphene, D. Pentazocine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Amongst opioid antagonists :- Naloxone is given iv or im, Nalmefene is given iv, im or sc, and Naltrexone is given orally.', 'role': 'assistant'}]