The correct option is E T cell
The thymus is the primary lymphoid organ where lymphocytes originate and/or mature. T-lymphocytes originate from lymphoid progenitor cells in thymus via three developmental stages, namely pro, pre and immature T cells. The immature T cells mature in thymus only. B cell originates and matures in red bone marrow, fibrinogen is the clotting factor 1 in blood and phagocytes are the type of WBC. Thus, the correct answer is E.