The correct option is D All of the above
Neutrophils are the most abundant WBCs and are phagocytic in nature. Macrophages are formed by the maturation of monocytes, that engulf foreign substances. Lymphocytes are B cells or T cells that have receptors on their surface to be able to bind to antigens.
So, all these three types of cells are associated with the immune system in one way or the other.
Thus, the correct answer is option D.