Which one of the following hypotheses may be sufficient to explain non precipitation in antigen-antibody system?

Neither monovalent antigen nor monovalent antibody (Fab:) can form a precipitin lattice. An antigen molecule containing closely repeating antigen determinants (e.g., a polysaccharide or a multi chained polymeric protein), can bind antibody to two determinants on a single particle; this "monogamous bivalency" inhibits precipitation. Fab2 divalent antibodies can precipitate antigens, though they lack Fc portions.