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: Surgery
Mayo's operation is done for - 
Select and explain. 
A. Spigelian hernia, B. Femoral hernia, C. Richer's hernia, D. Umbilical hernia
D: Umbilical hernia
Answer: D: Umbilical hernia 
Explanation: None