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
Which one has least mineralocorticoid activity ? 
Select and explain. 
A. Cortisol, B. Prednisolone, C. Fludrocortisone, D. Methyl prednisolone
D: Methyl prednisolone
Answer: D: Methyl prednisolone 
Explanation: None