AMC 10A 2008 Problem 7

The fraction

\dfrac{\left(3^{2008}\right)^{2}-\left(3^{2006}\right)^{2}}{\left(3^{2007}\right)^{2}-\left(3^{2005}\right)^{2}}

simplifies to which of the following?

Answer Choices
A. 1
B. \dfrac{9}{4}
C. 3
D. \dfrac{9}{2}
E. 9