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
Clamshell technique is required for: 
Select and explain. 
A. llio-cortico graft, B. llio-cancellous graft, C. Posterior iliac graft, D. Anterior iliac graft
B: llio-cancellous graft
Answer: B: llio-cancellous graft 
Explanation: None