Simplify the following.
${}^4\sqrt{256a^8{b}^9}$

• A. $4a^2{b}^3$
• B. $4a^2{b}^2{.}^4\sqrt{b}$
• C. $4a^4{b}^5$
• D. $4a^2{b}^2{.}^4\sqrt{b^3}$

Answer: (B)