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: Surgery
Mr. Ramu, a 49 yr old gentleman, undergoes a root canal procedure. Few days later he develops fever, weight loss, and anorexia. He is diagnosed with mitral valve prolapsed with mitral regurgitation. The most common organism implicated in causation of this condition is: 
Select and explain. 
A. Streptococcus pneumonia, B. Staphylococcus aureus, C. Viridans streptococci, D. Providencia stuaii
C: Viridans streptococci
Answer: C: Viridans streptococci 
Explanation: Viridans streptococci. (Braunwald, 15/e, pp 809-814, 882-885, 959, 1009, 1620.) The 30-year-old-female with mitral valve prolapse has developed subacute bacterial endocarditis. The likely etiologic agent is a viridans streptococci. Viridans streptococci cause most cases of subacute bacterial endocarditis. No other agent listed is likely to cause this infection.