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
The following diagnostic tests are useful for corresponding purposes, EXCEPT: 
Select and explain. 
A. Ziehl -Neelsen staining - Detection of mycobacteria, B. Immunofluorescence - Detection of Influenza virus, C. Specific IgM antibodies - Immunity against Rubella, D. Specific IgM antibodies - Detection of acute infection
C: Specific IgM antibodies - Immunity against Rubella
Answer: C: Specific IgM antibodies - Immunity against Rubella 
Explanation: Ziehl Neelsen is used for Mycobacterial detection. Rapid diagnosis of influenza is made by demonstration of viral antigen on the surface of nasopharyngeal cells by immunofluorescence. IgM antibodies are antibodies of primary response so it indicates acute/recent infection. Its production signify that immune response of individual is proper but does not mean that person has immunity against infection. Ref: Harrison's Principles of Internal Medicine, 18th Edition, Chapter 193