Solve the equation $\sin 9\theta=\sin \theta$

Question

$\begin{array}{1 1}(A)\;\theta=\large\frac{n\pi}{4},\frac{(2n+1)\pi}{10}\\(B)\;\theta=\large\frac{n\pi}{6},\frac{(2n+1)\pi}{8}\\(C)\;\theta=\large\frac{n\pi}{2},\frac{(3n+1)\pi}{10}\\(D)\;\theta=\large\frac{\pi}{12},\frac{(2n+1)\pi}{12}\end{array}$