While looking at a sample of blood in a microscope, you see a purple-stained cell that is markedly larger than a red blood cell (about two to three times larger).

It has a large kidney-shaped nucleus.

What type of blood cell is this?

B cells are a type of lymphocyte that originate from the bone marrow and are involved in humoral immunity.
When they encounter a foreign substance (antigen), they differentiate into plasma cells, which secrete antibodies.
Antibodies are proteins that bind to the antigen and neutralize it.
Choice A is wrong because megakaryocytes are large cells that produce platelets, not antibodies.
Choice C is wrong because antibodies are not cells, but products of plasma cells.
Choice D is wrong because T cells are another type of lymphocyte that originate from the thymus and are involved in cell-mediated immunity, not antibody production.

Macrophages are the main cells that clear out the cell debris by phagocytosis, a process that involves recognition, engulfment, and degradation of the disposable particles.

Macrophages are professional phagocytes that can be found in various tissues and organs, where they perform efferocytosis, the removal of dead and dying cells.

Choice A is wrong because lymphocytes are not phagocytes, but rather immune cells that mediate adaptive immunity by producing antibodies or killing infected cells.

Choice B is wrong because cytokines are not cells, but rather soluble molecules that regulate inflammation and immunity by acting as signals between cells.

Choice C is wrong because mast cells are not primarily involved in clearing cell debris, but rather in allergic reactions and innate immunity by releasing histamine and other mediators.