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

Question

( A ) $\sin^{-1} (\frac{\sqrt 3 }{4})$
( B ) $\frac{\pi}{3}$
( C ) $\sin^{-1} (\frac{1}{\sqrt 3 })$
( D ) $\frac{\pi}{6}$