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': 'Most common organism causing URTI in adult- \nSelect and explain. \nA. H. influenza, B. Staph. aureus, C. Strep. pneumonia, D. Strep. pyogenes', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]