计算 $\left(\begin{array}{llll}1 & 2 & 1 & 0 \\ 0 & 1 & 0 & 1 \\ 0 & 0 & 2 & 1 \\ 0 & 0 & 0 & 3\end{array}\right)\left(\begin{array}{rrrr}1 & 0 & 3 & 1 \\ 0 & 1 & 2 & -1 \\ 0 & 0 & -2 & 3 \\ 0 & 0 & 0 & -3\end{array}\right)$ 。
$\text{A.}$
$\text{B.}$
$\text{C.}$
$\text{D.}$