Answer:
The correct answer is d.
Explanation:
Regulatory T-cells are a class of T cells which are part of the immune system that suppresses immune response. They are called regulatory because they assist in "checking" the excesses/overreaction during immune response.
NOTE:
Neutrophils are phagocytic in nature; they ingest and destroy microorganisms or other foreign molecules.
Plasma cells synthesize antibodies which are produced in response to antigens. They are target foreign particles for digestion by other immune cells.
Macrophages are also phagocytic in nature usually found at sites of an infection.
