The correct option is
A Macrophages
All organisms are naturally gifted with the resistance to certain infections from birth and this natural mechanism is known as innate immunity. One of the major ways through which the immune system operates is by producing different kinds of cells. It is part of the cellular barriers of innate immunity.
Natural killer cells : They are a type of lymphocytes. They will phagocytose and kill bacterial and viral infected cells.
Monocytes : They are a type of white blood cells. They are large, amoeboid cells with a kidney shaped nucleus in blood smears. They remain in the blood for a short time and migrate to the tissues to form macrophages.
Macrophages : Macrophages have a long life span. Monocytes transform into macrophages with morphological and functional changes. They are strongly phagocytic to a wide variety of materials such as viable microorganisms, dead cells, cell debris etc.
Thrombocytes or platelets : They are present in blood and associated with blood clotting. This prevents leakage of blood in the areas of injuries.
Basophils : They are a type of white blood cells associated with inflammatory reactions like swelling and redness in the affected areas.