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
A patient of Rheumatic heart disease developed infective endocarditis after dental extraction. Most likely organism causing this is: 
Select and explain. 
A. Streptococcus viridans, B. S.epidermidis, C. S.aureus, D. Pneumococci
A: Streptococcus viridans
Answer: A: Streptococcus viridans 
Explanation: Following tooth extraction, Streptococcus viridans gets lodged into previously damaged valve.