This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
Antigen-antibody reaction is detected by 
Select and explain. 
A. ELISA, B. Southern blot, C. Nohern blot, D. Western blot
A: ELISA
Answer: A: ELISA 
Explanation: An enzyme-linked immunosorbent assay, also called ELISA or EIA, is a test that detects and measures antibodies in your blood. This test can be used to determine if you have antibodies related to ceain infectious conditions. Antibodies are proteins that your body produces in response to harmful substances called antigens. An ELISA test may be used to diagnose:HIV, which causes AIDSLyme diseasepernicious anemiaRocky Mountain spotted fever (RMSF)RotavirusSquamous cell carcinomaSyphilisToxoplasmosisVaricella-zoster virus, which causes chickenpox and shinglesRef: DM Vasudevan, 7th edition, page no: 453