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