If $\sin y = x \sin (a + y) $, then $\frac{dy}{dx}$ is :

Question

( A ) $\frac{\sin a}{\sin^2 (a+y)}$
( B ) $\frac{\sin^2(a-y)}{\sin a}$
( C ) $\frac{\sin^2(a+y)}{\sin a}$
( D ) $\sin a \sin^2 (a+y)$