If $\large\frac{\tan 3A}{\tan A}$$=a$ then $\large\frac{\sin 3A}{\sin A}$ is equal to :

Question

$$\begin {array} {1 1} (a)\;\frac{2a}{a+1} & \quad (b)\;\frac{2a}{a-1} \\ (c)\;\frac{a}{a+1} & \quad (d)\;\frac{a}{a-1} \end {array}$$