The A.M of first $n$ natural number is

Question

$\begin {array} {1 1} (A)\;\large\frac{1}{2} (n+1) & \quad (B)\;\large\frac{n}{2} \\ (C)\;\large\frac{1}{2} (n-1) & \quad (D)\;None\: of \: these \end {array}$