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
Longest acting glucocoicoids is ? 
Select and explain. 
A. Prednisone, B. Prednisolone, C. Coisone, D. Dexamethasone
D: Dexamethasone
Answer: D: Dexamethasone 
Explanation: Ans. is 'd' i.e., Dexamethasone