This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Pediatrics
[{'content': 'Most common cause of pneumonia in children less than 2 years is ? \nSelect and explain. \nA. RSV, B. Streptococcus aureus, C. Staphylococcus aureus, D. Klebsiella', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Respiratory syncytial virus is the most impoant cause of pneumonia in children less than 2 years of age.At other ages ,influenza, parainfluenza, adeno virus are common. Bacteria causing pneumonia are klebsiella, S.pneumonia, E.coli, H.influenza, staphylococci, Atypical organisms like Mycoplasma and Pneumocystis carinii. Ref : ESSENTIAL PEDIATRICS,O.P.GHAI,PG NO:352,7th edition', 'role': 'assistant'}]