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': 'Reactive ahritis is usually caused by \nSelect and explain. \nA. Shigella flexneri, B. Shigella boydii, C. Shigela shiga, D. Shigela dysentriae', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Shigella Flexneri Organisms that have been associated with ReiterAhritis include the following: C trachomatis (L2b serotype) Ureaplasma urealyticum Neisseria gonorrhoeae Shigella flexneri Salmonella enterica serovars Typhimurium Mycoplasma pneumoniae Mycobacterium tuberculosis Yersinia enterocolitica and pseudotuberculosis Campylobacter jejuni Clostridium difficile Beta-hemolytic (example, group A) and viridans streptococci", 'role': 'assistant'}]