<prompt> Which of the organisms most commonly causes reactive ahritis?Ureaplasma urealyticumGroup A beta hemolytic streptococciBorrelia burggorferiChlamydia  <response>: 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. 