This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pathology
Complement Fixation test is: 
Select and explain. 
A. WIDAL, B. Coombs test, C. Wassermann reaction, D. VDRL
C: Wassermann reaction
Answer: C: Wassermann reaction 
Explanation: The complement fixation test (CFT) was extensively used in syphilis serology after being introduced by Wasserman in 1906. However, there is now a trend to replace the CFT with the simple flocculation tests. Although CFT is considered to be a relatively simple test, it is a very exacting procedure because 5 variables are involved. In essence the test consists of two antigen-antibody reactions, one of which is the indicator system. REF: ROBBINS pathology 10th edition