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': 'Least common cause of endocarditis is \nSelect and explain. \nA. A.S.D., B. P.D.A., C. T.O.F., D. V.S.D.', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]