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: Microbiology
[{'content': 'A patient of Rheumatic heart disease developed infective endocarditis after dental extraction. Most likely organism causing this is: \nSelect and explain. \nA. Streptococcus viridans, B. S.epidermidis, C. S.aureus, D. Pneumococci', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Following tooth extraction, Streptococcus viridans gets lodged into previously damaged valve.', 'role': 'assistant'}]