Which of the following are secondary lymphoid organs?

Spleen, lymph nodes, tonsils, and Peyer’s patches are examples of secondary lymphoid organs. Bone marrow and thymus are primary lymphoid organs.
The secondary lymphoid organs provide the sites for interaction of lymphocytes with the antigen, which then proliferate to become effector cells. They serve as sites for the accumulation and activation of immune cells, particularly lymphocytes.