This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Systemic Bacteriology (Haemophilus, Yersinia, Spirochaetes, Ricketssia, Chlamydia, Mycoplasma and Miscellaneous Bacteria), Subject name: Microbiology
[{'content': 'Bacteria showing antigenic variation- \nSelect and explain. \nA. Yersinia, B. Bordetella, C. Brucella, D. Borrelia', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Borellia cause Relapsing fever Reason for relapse is antigenic variation by changing outer surface protein. Borellia readily undergoes antigenic variation reason for relapse', 'role': 'assistant'}]