The geometric mean of $ 2.262.....2^n$ is

Question

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