This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
Antigen antibody precipitation is maximally seen in which of the following ? 
Select and explain. 
A. Excess of antibody, B. Excess of antigen, C. Equivalence of antibody and antigen, D. Antigen Hapten interaction
C: Equivalence of antibody and antigen
Answer: C: Equivalence of antibody and antigen 
Explanation: According to lattice hypothesis, precipitation results when a large lattice is formed consisting of alternating antigen and antibody molecules. This is possible only at the zone of equivalence. At the zone of equivalence, antigen and antibody are in optimum propoion. Lattice formation and visible reactions are enhanced. Reference: Anathanarayan & paniker's 9th edition, pg no:105 <\p>