AHSME 1975 Problem 4

If the side of one square is the diagonal of a second square, what is the ratio of the area of the first square to the area of the second? $\textbf{(A)}\ 2 \textbf{(B)}\ \sqrt2 \textbf{(C)}\ 1/2 \textbf{(D)}\ 2\sqrt2 \textbf{(E)}\ 4$