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
[{'content': "Which one of the following hypotheses may be sufficient to explain non precipitation in antigen-antibody system? \nSelect and explain. \nA. The antigen has a multivalent determinant, B. The antigen has a single, non-repeated determinant, C. The antibody has been cleaved to divalent Fab' ligands, D. The antibody has been cleaved to divalent Fab'2 ligands", 'role': 'user'}, {'content': 'Answer: C \nExplanation: 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.', 'role': 'assistant'}]