Answer: Option B. "T Cell maturation"
Step-by-step explanation:
T-cell, also known as T lymphocyte, are primary type of leukocyte or white blood cell important part of the immune system.
Bone marrow is the origin of T-cells and then get mature in the thymus. In thymus, T- cells differentiate or multiply into regulatory, or cytotoxic T-cells helper, or act as memory T-cells.
T-cells then move in lymphatic system, once get stimulated by appropriate antigen, helper T-cells secrete cytokines that stimulate antibody-producing cells called B cells. Regulatory T-cells control immune reactions while Cytotoxic T-cells kill infected cells or cancer cells.
Hence, the correct answer is Option B.