Eosinophils are associated with allergic reactions and release histaminase, destructive enzymes, so (a) matches with (iii). Basophils secrete histamine, serotonin, heparin etc. and are involved in inflammatory reactions, so (b) matches with (iv). Neutrophils are phagocytic cells; so (c) matches with (ii). Both B and T lymphocytes are responsible for immune responses of the body, so (d) matches with (i).