Answer
B. 8
Work Step by Step
As shown on page 445, we know that $a^{\frac{m}{n}}=\sqrt[n] a^{m}=(\sqrt[n] a)^{m}$.
Therefore, $4^{\frac{3}{2}}=\sqrt[2] 4^{3}=\sqrt 4^{3}=(\sqrt 4)^{3}=2^{3}=8$.
We know that $\sqrt 4=2$, because $2^{2}=4$.