1. In the geometric sequence $\left\{a_{n}\right\}$, let $S_{n}=a_{1}+a_{2}+\cdots+$ $a_{n}$, it is known that $a_{5}=2 S_{4}+3, a_{6}=2 S_{5}+3$. Then the common ratio $q$ of this sequence is ( ).
(A) 2
(B) 3
(C) 4
(D) 5
$\begin{array}{c}-\sqrt{-1}\} \\ a_{6}-a_{5}=\left(2 S_{5}+3\right)-\left(2 S_{4}+3\right)=2\left(S_{5}-S_{4}\right) \\ =2 a_{5} \text {. Therefore, } a_{6}=3 a_{5} \text {, so } q=3 .\end{array}$