In a Rhombus $PQRS$, if $PQ=PR$, then $\angle{PQR} =$

Question

$\begin{array}{1 1} (a)\; 120^{\circ} \\ (b)\; 90^{\circ} \\ (c)\;60^{\circ} \\ (d)\; \text{none of the above } \end{array}$