If $n$ is even,then the greatest coefficient in the expansion of $(x+a)^n$ is

Question

$\begin{array}{1 1}(A)\;nC_{\Large\frac{n}{2}+1}\\(B)\;nC_{\Large\frac{n}{2}-1}\\(C)\;nC_{\Large\frac{n}{2}}\\(D)\;\text{None of these}\end{array}$