A current-element ($I\vec{dl}$) of mass per unit length ($m$) is held in air as shown in the figure. After withdrawing the support, it will remain suspended in its position, when subjected to an external magnetic field $\vec{B}$ equal to : (A) $\frac{mgdl}{I}\hat{k}$ (B) $\frac{mg}{I}\hat{j}$ (C) $-\frac{mg}{I\,dl}\hat{i}$ (D) $-\left(\frac{I\,dl}{mg}\right)\hat{k}$