6. $6^{11}+C_{11}^{1} 6^{10}+C_{11}^{2} 6^{9}+\cdots+C_{11}^{10} 6-1$ when divided by 8 yields a remainder of ( ).
(A) 0
(B) 2
(C) 3
(D) 5
6.D.
$$
\begin{array}{l}
6^{11}+C_{11}^{1} 6^{10}+\mathrm{C}_{11}^{2} 6^{6}+\cdots+C_{116}^{10} 6-1 \\
=(6+1)^{11}-2=7^{11}-2 . \\
7^{11}-2=7^{11}+1-3 \\
=(7+1)\left(7^{10}-7^{9}+\cdots-7+1\right)-3 \\
=8\left(7^{10}-7^{9}+\cdots-7+1\right)-3 \\
=8\left(7^{10}-7^{9}+\cdots-7\right)+5 .
\end{array}
$$

Therefore, the remainder when the original expression is divided by 8 is 5.