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
The drug of choice for Addison's disease is: 
Select and explain. 
A. Hydrocoisone, B. Betamethasone, C. Dexamethasone, D. Prednisolone
A: Hydrocoisone
Answer: A: Hydrocoisone 
Explanation: Hydrocoisone