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 above statements, choose the most appropriate answer from the options given below :

Which of the following cells are associated with immune system of body

Lacking of $B$-cells and $T$-cells is known as

The thymus is a lobed organ located near the $…A…$ and beneath the $…B… $ The most appropriate combination for $\mathrm{A}$ and $\mathrm{B}$ is

Which is incorrect pair on basis of its role in immune system?