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: Unknown
Nichol's strain is used in: 
Select and explain. 
A. TP HA test, B. TPI test, C. VDRL, D. FTA-ABS
B: TPI test
Answer: B: TPI test 
Explanation: Treponema pallidum immobilization (TPI) test, considered both as a qualitative and as a quantitative test, and then various specific aspects of passage of the Nichols strain of treponeme in rabbit testes. a serological test for syphilis in which a solution containing the living causative spirochete (Treponema pallidum) is combined with serum in the presence of complement with immobilization of the active spirochetes indicating a positive result