Some T-cells are called cells because they destroy antigens

T cell, also called T lymphocyte, type of leukocyte (white blood cell) that is an essential part of the immune system. ... T cells are one of two primary types of lymphocytes—B cells being the second type—that determine the specificity of immune response to antigens (foreign substances) in the body.

T cells are one of the types of lymphocytes that develop in the thymus. Antibodies are proteins made and released by B cells against foreign pathogens  

Explanation:

meaning T-cell antigen receptors are found only on the cell membrane. For this reason, T-cell receptors were difficult to isolate in the laboratory and were not identified until 1983. T-cell receptors consist of two polypeptide chains. The most common type of receptor is called alpha-beta because it is composed of two different chains, one called alpha and the other beta. A less common type is the gamma-delta receptor, which contains a different set of chains, one gamma and one delta. A typical T cell may have as many as 20,000 receptor molecules on its membrane surface, all of either the alpha-beta or gamma-delta type.

i agree d is most definitely correct!