Final answer:
The most common lymphocytes derived from bone marrow progenitor cells that mature in the thymus gland are T cells.
Step-by-step explanation:
Most lymphocytes found in the circulating blood that are derived from bone marrow progenitor cells that mature in the thymus gland are T cells. T cells migrate from the bone marrow to the thymus where they undergo maturation. B cells, on the other hand, mature in the bone marrow itself. Both B cells and T cells are types of lymphocytes that play a crucial role in the immune response.