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 MOST COMMON causative organism for community acquired pneumonia is: \nSelect and explain. \nA. Streptococcus pneumoniae, B. Haemophilus influenzae, C. Mycoplasma pneumoniae, D. Chlamydia pneumoniae', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Although Streptococcus pneumoniae is most common pathogen causing community aquoired pneumonia. Data suggest that a virus may be responsible for up to 18% of cases of CAP that require admission to the hospital. Ref: Harrison, E-18,P-2131.', 'role': 'assistant'}]