Given the statements:
- $\text{P}$ is the sister of $\text{Q.}$
- $\text{Q}$ is the husband of $\text{R.}$
- $\text{R}$ is the mother of $\text{S.}$
- $\text{T}$ is the husband of $\text{P.}$
Based on the above statements, we can draw the diagram.

$\therefore \;\text{T}$ is ${\color{Blue}{\text{an uncle}}}$ of $\text{S}.$
Correct Answer $:\text{B}$