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: Medicine
Antigen antiboey reaction is detected by: 
Select and explain. 
A. ELISA, B. Southern blot, C. Nohern blot, D. All
A: ELISA
Answer: A: ELISA 
Explanation: A i.e. ELISA