A value of $\theta$ for which $ \large\frac{2+3 i \sin \theta}{1- 2 i \sin \theta}$ is purely imaginary , is

Question

$\begin{array}{1 1}(1) \large\frac{\pi}{3} \\ (2) \large\frac{\pi}{6} \\ (3) \sin ^{-1} \large\frac{\sqrt 3}{4} \\ (4) \sin^{-1}\bigg(\large\frac{1}{\sqrt 3} \bigg) \end{array} $