The correct answer is option no. ($4$) as both statements $I$ and $II$ are correct.

In humans, the bone marrow is the main lymphoid organ where all blood cells including lymphocytes are produced.

Both bone-marrow and thymus provide micro-environments for the development and maturation of $\mathrm{T}$ lymphocytes.

Options $(1)$, ($2$) and ($3$) are incorrect.