Which of the following are secondary lymphoid organs?
- A and D only
- A and B only
- B and C only
- B and D only
Answer
(3) B and C only
Solution
Primary lymphoid organs are bone marrow and thymus, where immature lymphocytes differentiate and mature. Secondary lymphoid organs include spleen, lymph nodes, tonsils, Peyer's patches of small intestine, and appendix. Therefore, tonsils (B) and spleen (C) are secondary lymphoid organs.
Answer: (3)