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
Most common organism associated with reactive arthritis is? 
Select and explain. 
A. Staphylococcus, B. Shigella, C. Chlamydia, D. Yersinia
C: Chlamydia
Answer: C: Chlamydia 
Explanation: None