解线性方程组
1. $\left\{\begin{array}{l}x_1+x_2-3 x_3-x_4+x_5=0 \\ 3 x_1-x_2+x_3+4 x_4+3 x_5=0 \\ x_1+5 x_2-9 x_3-8 x_4+x_5=0\end{array}\right.$
2. $\left\{\begin{array}{l}x_1-2 x_2+2 x_3-x_4=1 \\ 2 x_1-4 x_2+8 x_3=2 \\ -2 x_1+4 x_2-2 x_3+3 x_4=3 \\ 3 x_1-6 x_2-6 x_4=4\end{array}\right.$
$\text{A.}$
$\text{B.}$
$\text{C.}$
$\text{D.}$