Right choice is (d) Cytokine
To explain: Monoclonal antibodies are modified to deliver any toxin, radioisotope, cytokine or other active conjugates used for treatment purposes. Bispecific antibodies that can bind with their Fab regions both to the target antigen and to a conjugate or effector cell are also produced. Antibodies similar to human antibodies are produced so that they don’t suffer immune rejections.