Which of the Following Statements Is Correct

Which of the following statements is correct?

A) In adults the mature T-cell repertoire is self-renewing and long-lived and does not require a thymus for the provision of new T cells.
B) T cells and B cells are both short-lived cells and require continual replenishment from primary lymphoid organs.
C) The human thymus is not fully functional until age 30,at which time it begins to shrink and atrophy.
D) In DiGeorge syndrome the bone marrow takes over the function of the thymus and produces mature peripheral T cells.
E) None of the above statements is correct.