Ans: B
$\begin{array}{cl}
& \dfrac{(2^n)(8^{3n})}{64^n} \\
= & \dfrac{2^n \cdot (2^3)^{3n}}{(2^6)^n} \\
= & \dfrac{2^n \cdot 2^{9n}}{2^{6n}} \\
= & 2^{n+9n-6n} \\
= & 2^{4n} \\
= & (2^2)^{2n} \\
= & 4^{2n}
\end{array}$
