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: Pharmacology
[{'content': "The drug of choice for Addison's disease is: \nSelect and explain. \nA. Hydrocoisone, B. Betamethasone, C. Dexamethasone, D. Prednisolone", 'role': 'user'}, {'content': 'Answer: A \nExplanation: Hydrocoisone', 'role': 'assistant'}]