If the mean of the set of numbers $ x_1, x_2.....x_n$ is $ \overline x$ then mean of the numbers $ x_i+2i \: \: 1 \leq i \leq n $ is

Question

$\begin {array} {1 1} (A)\;\overline x + 2n & \quad (B)\;\overline x +n+1 \\ (C)\;\overline x +2 & \quad (D)\;\overline x+n \end {array}$