AHSME 1952 Problem 6

The difference of the roots of $x^2-7x-9=0$ is: $\textbf{(A) \ }+7 \textbf{(B) \ }+\frac{7}{2} \textbf{(C) \ }+9 \textbf{(D) \ }2\sqrt{85} \textbf{(E) \ }\sqrt{85}$