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: Medicine
[{'content': 'High oral: Parenteral activity ratio is seen with - \nSelect and explain. \nA. Morphine, B. Diacetyl morphine, C. Oxymorphine, D. Methadone', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]