3. If the 5th term in the expansion of $\left(x \sqrt{x}-\frac{1}{x}\right)^{6}$ is 5, then $\lim _{n \rightarrow \infty}\left(x^{-1}+x^{-3}+\cdots+x^{1-2 n}\right)$ equals ( ).
A. $\frac{3}{8}$
B. $\frac{9}{8}$
C. 1
D. $\frac{1}{2}$