计䈯: $\left(\begin{array}{cccc}1 & 2 & 3 & 4 \\ 0 & 2 & -1 & 1 \\ 1 & -1 & 2 & 5\end{array}\right)+\frac{1}{2}\left(\begin{array}{cccc}2 & 1 & 4 & 10 \\ 0 & -1 & 2 & 0 \\ 0 & 2 & 3 & -2\end{array}\right)$
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$\text{B.}$
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