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': 'Most common cause of gangrene of foot of 30-years old farmer who is a chronic smoker \nSelect and explain. \nA. Raynaud’s disease, B. Myocardial infarction, C. Atherosclerosis, D. Thromboangitis obliterans', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]