Which of the following is not a lymphoid tissue?

1. Spleen         
2. Tonsils         
3. Pancreas               
4. Thymus

(c) Lymphoid organs are the organs where origin and/or maturation and proliferation of

lymphocytes occur.

The secondary lymphoid organs provide the sites for interaction of lymphocytes with
the antigen, which then proliferate to becomes effector cells,

Appendix is sometime not considered as the lymphoid organ, as it has been proposed
to be a vestigial structure connected to the cecum, located near the junction of the
small intestine and the large intestine.