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: Microbiology
Which is not a heterophile agglutination test ? 
Select and explain. 
A. Weil Felix test, B. Widal test, C. Paul Bunnell test, D. Streptococcus
B: Widal test
Answer: B: Widal test 
Explanation: Ans. is 'b' i.e., Widal test Heterophilic agglutination reaction . Some organisms of different class or species share closely related antigens. . When serum containing agglutinin (antibody) of one organism gives agglutination reaction with antigen of other organism, it is called heterophilic agglutination test. Examples are . Streptococcus M.G. agglutination test for primary atypical pneumonia. . Weil - Felix reaction for typhus fever . Paul Bunnell test fin- IMN.