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
[{'content': 'Which is the most common material used for grafting below inguinal aeries? \nSelect and explain. \nA. Saphenous vein graft (upside - down), B. PTFE, C. Dacron, D. Teflon', 'role': 'user'}, {'content': "Answer: A \nExplanation: For blockage fuher down the leg either a femoral popliteal or femoral distal procedure may be performed. Long saphenous vein is the graft of choice which may be used with its valves destroyed by a special valve cutting instrument or reversed so that the valves do not interfere with the bold flow. Ref: Schwaz's Principles of Surgery, 9th Edition, Chapter 23; Surgical Talk: Revision in Surgery By Andrew Goldberg, Page 238; Mastery of Vascular and Endovascular Surgery By Gerald B. Zelenock, Page 417", 'role': 'assistant'}]