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': "Dark ground microscopy is used for: \nSelect and explain. \nA. TPI, B. Kahn's test, C. FTA-ABS, D. VDRL", 'role': 'user'}, {'content': 'Answer: A \nExplanation: In TPI test , the serum of patient with complement and T.pallidum maintained in a complex medium anaerobically . If the antibodies are present , the treponemes are rendered non motile, when examined under dark ground illumination Kahn test and VDRL test are non specific antigen antibody test ,cardiolipin antigen is used. FTA-ABS is specific antigen antibody test', 'role': 'assistant'}]