The correct option is A Lymphocyte
Monocytes are a type of WBCs. Monocytes mature in different types of macrophages at different locations. Monocytes and their macrophages serve three main functions as phagocytosis, antigen presentation and cytokine production.
Lymphocytes are B-cells or T-cells and they have receptors on their surface and are able to bind antigens and thus help the foreign substance to get removed from the body. They are not phagocytic in nature.
Mast cell is the part of immune system that contains granules rich in histamine and heparin. They can also participate in the direct killing of organisms by phagocytosis.
Neutrophils are the most abundant type of WBCs. They are phagocytic in nature and are able to engulf foreign substances (like bacteria).
Thus, the correct answer is option B.