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': 'The organism most commonly implicated in the causation of subacute bacterial endocarditis is: \nSelect and explain. \nA. S. albus, B. S. Aureus, C. S. typhi, D. S. Viridans', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]