The correct answer is T lymphocyte.
A lymphocyte refers to a type of white blood cell produced in the bone marrow. Lymphocytes are the primary actors of the immune system in the body. They are of three types namely, the natural killer cells, B lymphocytes and the T lymphocytes. B lymphocytes are produced in the bone marrow and mature in the bone marrow, whereas the T lymphocytes are produced in the bone marrow and migrate to the organ called the thymus.
T lymphocyte is involved in rendering the cell mediated immunity. It refers to the immunity against the foreign substances by the action of the cells differentiated by T cells and not by the antibodies. They are further divided into helper T cells, cytotoxic T cells, effector T cells, natural killer T cells, memory T cells and others. They recognize the antigens by the presence of T celll receptors.