Read the following passage and answer the question :
The primary lymphoid organs are bone marrow and thymus, where immature lymphocytes differentiate into antigen sensitive lymphocytes. They migrate to secondary lymphoid organ like spleen, lymph nodes, tonsils, Peyer’s patches of small intestine and appendix. All blood cells including lymphocytes are produced in bone marrow which is main lymphoid organ. Spleen is large reservoir of erythrocytes. It is large bean shaped organ mainly containing lymphocyte and phagocyte. It acts as filter of blood by trapping blood borne micro organism. Lymph nodes are small solid structures located at different points along lymphatic system. Antigens trapped in lymph node are responsible for activation of lymphocytes present there and cause the immune response. There is lymphoid tissue located within. Lining of major tracts like respiratory, digestive and urogenital tracts called mucous associated lymphoid tissue (MALT).
Which of the following is NOT secondary lymphoid organ?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Thymus
Secondary lymphoid organs are where mature lymphocytes meet antigens and multiply. The primary lymphoid organs, bone marrow and thymus, are where immature lymphocytes become antigen-sensitive.
Option (1) Tonsils — A secondary lymphoid organ.
Option (2) Thymus — Not a secondary lymphoid organ. The thymus is a primary lymphoid organ. It is a lobed organ near the heart, beneath the breastbone. With the bone marrow, it provides the setting in which T-lymphocytes develop and mature. Only after this do the lymphocytes move to the secondary organs, such as the tonsils, appendix and Peyer’s patches, to meet antigens.
Option (3) Appendix — A secondary lymphoid organ.
Option (4) Peyer’s Patches — A secondary lymphoid organ.
Note 1: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
Note 2: A similar question was also asked in CUET (UG) 2026 on 15-05-2026 (Slot 1), and in CUET (UG) 2025 on 16-05-2025 (Slot 1).