This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Antigen-antibody reaction, Subject name: Microbiology
Which is a example of antigen - antibody reaction- 
Select and explain. 
A. Flocculation reaction, B. Precipitation, C. Agglutination, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Ans. is 'd' i.e., All of the above o Important antigen-antibody reactions in laboratory are:-i) Precipitation/Flocculationii) Agglutinationiii) CFTv) Neutrilization reaction