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: Skin
M.C. cause of Nongonococcal Urethritis 
Select and explain. 
A. Chlamydia, B. Mycoplasma, C. Trichomonas, D. Gram negative rod
A: Chlamydia
Answer: A: Chlamydia 
Explanation: A i.e. Chlamydia