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 glucocorticoids is: 
Select and explain. 
A. Prednisone, B. Prednisolone, C. Cortisone, D. Dexamethasone
D: Dexamethasone
Answer: D: Dexamethasone 
Explanation: None