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
Causative agent for rheumatoid ahritis is: 
Select and explain. 
A. Mycoplasma, B. Mycobacaterium avium, C. Yersinia, D. Herpes virus
A: Mycoplasma
Answer: A: Mycoplasma 
Explanation: Answer is A (Mycoplasma) The true causative agent for Rheumatoid ahritis is not known. Mycoplasma has been suggested as a possible causative agent, and hence is the single best answer of choice