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': 'Mural thrombi are thrombi \nin \nSelect and explain. \nA. Heart chamber, B. Valve cusp, C. Vein, D. Arteries', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]