Select the option that contains only secondary lymphoid organs.

Lymphocytes are sensitive to .........

Which is an example of active immunity?

Given below are two statements:
Statement $I$: Bone marrow is the main lymphoid organ where all blood cells including lymphocytes are produced.
Statement $II$: Both bone marrow and thymus provide micro-environments for the development and maturation of $T$-lymphocytes.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which lymphoid organ decreases in size with increasing age?

What is the full form of $MALT$?