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
Most common organism causing URTI in adult- 
Select and explain. 
A. H. influenza, B. Staph. aureus, C. Strep. pneumonia, D. Strep. pyogenes
D: Strep. pyogenes
Answer: D: Strep. pyogenes 
Explanation: None