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: Pathology
[{'content': 'Most common cause of systemic thromboembolism is? \nSelect and explain. \nA. Paradoxical emboli, B. Intracardiac murals, C. Aortic aneurysms, D. Unknown origin', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Most systemic emboli (80%) arise from intracardiac mural thrombi; two-thirds of these are associated with left ventricular infarcts and another 25% with dilated left atria (e.g.secondary to mitral valve disease). The remainder originate from\xa0aortic\xa0aneurysms,\xa0thrombi\xa0overlying\xa0ulcerated\xa0atherosclerotic\xa0plaques,\xa0fragmented\xa0valvular\xa0vegetations, or the venous system (paradoxical emboli); 10% to 15% of systemic emboli are of unknown origin.', 'role': 'assistant'}]