The author supports the theory of cell-mediated reactions primarily by ______.
A.pointing out a contradiction in the assumption leading to the antigen-antibody theory
B.explaining how cell mediation accounts for phenomena that the antigen-antibody theory cannot account for
C.revealing new data that scientists arguing for the antigen-antibody theory have continued to ignore
D.showing that the antigen-antibody theory fails to account for the breakup of antigens