Which of the following is equivalent to the expression $\frac{a^{-2}b^{3}}{ab^{-1}}$ ?  $\textasciitilde$ 
选项为:A:$\frac{a^{3}}{b^{4}}$  B:$\frac{b^{4}}{a^{3}}$  C:$a^{-1}b^{2}$  D:$\frac{1}{a^{2}b^{3}}$  请回答其中一个选项.