Which portion of the lobes of the thymus gland contains lymphoid stem cells that divide rapidly, producing daughter cells that mature into T cells and migrate into the medulla?

The correct answer is - cortex

Explanation:

Thymus is the primary lymphoid organ where the development and maturation of T cell takes place. Thymus is bilobed and each lobe is divided into lobule which has two compartments a cortex (outer) and a medulla (inner).

The immature T progenitor cells reach to cortex region of thymus where their growth and differentiation occur. In the cortex, these T progenitor cells become mature and then migrates to the medullary region where they go thymic selection after encountering macrophages and dendritic cells. So the correct answer is cortex.