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: Psychiatry
[{'content': 'Drug of choice for substitution therapy in morphine dependence- \nSelect and explain. \nA. Methadone, B. Clonidine, C. Naloxone, D. Nalmefene', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Methadone", 'role': 'assistant'}]