6. Given a geometric sequence $\left\{a_{n}\right\}$ with common ratio $q$, compare $a_{9} S_{8}$ and $a_{8} S_{9}$
(B) $a_{9} S_{8}<a_{8} S_{9}$
(C) $a_{9} S_{8}=a_{8} S_{9}$
(D) It depends on the value of $a_{1}$
$\begin{array}{l}\text { 6. A. } \\ \begin{array}{l}a_{9} S_{8}-a_{8} S_{9} \\ =\frac{a_{1}^{2}}{1-q}\left[q^{8}\left(1-q^{8}\right)-q^{7}\left(1-q^{9}\right)\right] \\ =-a_{1}^{2} q^{7}>0 .\end{array}\end{array}$

The translation is as follows:

$\begin{array}{l}\text { 6. A. } \\ \begin{array}{l}a_{9} S_{8}-a_{8} S_{9} \\ =\frac{a_{1}^{2}}{1-q}\left[q^{8}\left(1-q^{8}\right)-q^{7}\left(1-q^{9}\right)\right] \\ =-a_{1}^{2} q^{7}>0 .\end{array}\end{array}$