This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardio thoracic surgery  , Subject name: Surgery
[{'content': 'Coronary graft is most commonly taken from ? \nSelect and explain. \nA. Femoral vein, B. Saphenous vein, C. Axillary vein, D. Cubital vein', 'role': 'user'}, {'content': "Answer: B \nExplanation: The long saphenous vein is the most common vein used as it is straightforward,provides good length & is easy to handle.The 10 year patency rate is repoed to be 50-60%,with10-15% occluding in one year.Other grafts used include left internal mammary aery or internal thoracic aery,sho saphenous vein,cephalic vein,radial aery,gastroepiploic aery,inferior epigastric aery Reference:Bailey & Love's sho practise of surgery,25th edition,page no:856", 'role': 'assistant'}]