If $\alpha$ is $n^{th}$ root of unity,the value of $1+2\alpha+3\alpha^2+...$ upto n terms is equal to

Question

$\begin{array}{1 1}(A)\;-\large\frac{2n}{(1-\alpha)^2}\\(B)\;-\large\frac{n}{(1-\alpha)}\\(C)\;-\large\frac{2n}{(1-\alpha)}\\(D)\;-\large\frac{n}{(1-\alpha)^2}\end{array}$