If $\theta$ is an acute angle and the vector $(\sin \theta) \hat{i} + (\cos \theta) \hat{j}$ is perpendicular to the vector $\hat{i}- \sqrt{3} \hat{j}$ ,then $\theta$ is equal to :

Question

( A ) $\frac{\pi}{5}$
( B ) $\frac{\pi}{4}$
( C ) $\frac{\pi}{6}$
( D ) $\frac{\pi}{3}$