According to the hypothesis of the author, after a successful liver transplant, the reason that rats do not reject further transplants of other organs from the same donor is that the A. transplantation antigens of the donor and the recipient become matched. B. lymphocytes of the recipient are weakened by the activity of the transplanted liver. C. subsequently transplanted organ is able to repair the damage caused by the recipient's immune-response reaction. D. transplanted liver continues to be the primary locus for the recipient's immune-response reaction. E. recipient is unable to manufacture the lymphocytes necessary for the immune-response reaction.