At the molecular level, which property of antibodies most directly enables the formation of visible antigen–antibody lattices in agglutination and precipitation assays?

• A. The glycosylation pattern on the Fc region which directly causes antigens to aggregate through carbohydrate bridging.
• B. Antibody-mediated complement fixation which is required to clump antigens together into visible aggregates in both precipitation and agglutination assays.
• C. Multivalency (multiple antigen-binding sites) that allows antibodies to bind two or more antigen epitopes simultaneously, forming cross-links between antigens.
• D. The enzymatic activity of antibodies that polymerizes antigen molecules into large insoluble complexes independent of binding valency.

Answer: (C)