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: Medicine
[{'content': 'Most common cause of acute arterial occlusion \nSelect and explain. \nA. Pulmonary emboli, B. Atherosclerosis plaque, C. Emboli atrial fibrillation, D. Thrombosis of aneurysm', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]