Model Paper 9 — NEET STD 11 Science — Question

A.  All of these
Explanation:
The primary lymphoid organs are bone marrow and thymus where immature lymphocytes differentiate into antigen-sensitive lymphocytes. After maturation, the lymphocytes migrate to secondary lymphoid organs like the spleen, lymph nodes, tonsils, Peyer's patches of the small intestine and appendix. The secondary lymphoid organs provide the sites for interaction of lymphocytes with the antigen, which then proliferate to become effector cells. There is lymphoid tissue also located within the lining of the major tracts (respiratory, digestive, and urogenital tracts) called mucosa-associated lymphoid tissue (MALT). It constitutes about 50 percent of the lymphoid tissue in the human body.