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': 'Which of the organisms most commonly causes reactive ahritis? \nSelect and explain. \nA. Ureaplasma urealyticum, B. Group A beta hemolytic streptococci, C. Borrelia burggorferi, D. Chlamydia', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Answer is D (Chlamydia): Amongst the options provided Chlamydia is the most commonly implicated agent in Reactive ahritis. `Chlamydia Trachomatis is by far the most common cause of urethritis and of reactive ahritis following urethritis.', 'role': 'assistant'}]