Ans: C
$\begin{array}{cl}
& \dfrac{2}{5-4x}-\dfrac{1}{5+4x} \\
= & \dfrac{2(5+4x)}{(5-4x)(5+4x)} -\dfrac{5-4x}{(5+4x)(5-4x)} \\
= & \dfrac{10+8x-5+4x}{(5+4x)(5-4x)} \\
= & \dfrac{5+12x}{25-16x^2}
\end{array}$
