Basophils have three lobed nucleus and a smaller number of coarse granules. They secrete histamine, serotonin, heparin, etc., and are involved in inflammatory reactions. Lymphocytes are smaller in size having round nucleus. They are of two major types - ' B ' and ' T ' lymphocytes. Both B and T lymphocytes are responsible for immune responses of the body. Neutrophils are the most abundant cells and are phagocytic in nature which destroy foreign organisms entering the body. They are polymorphic and have multi-lobed nucleus. Monocytes are the largest of all WBCs. They are motile, phagocytic in nature. Their life span is about 10−20hrs. 
Related Theory There are two types of WBC - granulocytes and agranulocytes. Neutrophils, eosinophils and basophils are different types of granulocytes, while lymphocytes and monocytes are the Agranulocytes.