The term affinity refers to the strength of attraction between a single antigenic determinant and a
corresponding antigen binding site. The term avidity refers to the total strength of the attraction between an
antibody and a multivalent antigen. The reaction between an IgM molecule (which has 10 antigen binding
sites), and a multivalent antigen is therefore much stronger than that of an IgG antibody (which has only 2
antigen binding sites).
Avidity is best described by which of the following statements: