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
Graft used in infra inguinal by pass is - 
Select and explain. 
A. PTFE, B. Dacron, C. Autologous vein, D. Autologous artery
C: Autologous vein
Answer: C: Autologous vein 
Explanation: None