Select the correct set of primary lymphoid organs in the human body.

The primary lymphoid organs are the bone marrow and the thymus, where immature lymphocytes differentiate into antigen-sensitive lymphocytes. The spleen, lymph nodes, tonsils, Peyer’s patches of small intestine and the appendix are the secondary lymphoid organs. The secondary lymphoid organs provide sites for the interaction of lymphocytes with the antigen, which then proliferate to become effector cells.