Calculate the mean deviation about the mean of the set of first n natural numbers when n is odd number.

Question

$\begin{array}{1 1}(A)\;\sqrt {\large\frac{n^2-1}{12}}\\(B)\;\large\frac{n^2-1}{4n}\\(C)\;0\\(D)\;\large\frac{n-1}{12}\end{array}$