The coefficient of $x^n$ in the expansion of $(1+x)^{2n}$ and $(1+x)^{2n-1}$ are in the ratio

Question

$\begin{array}{1 1}(A)\;1 : 2\\(B)\;1 : 3\\(C)\;3 : 1\\(D)\;2 : 1\end{array} $