Let $\mathrm{A}=\left(\begin{array}{c}100 \\ 210 \\ 321\end{array}\right)$. If $u_{1}$ and $u_{2}$ are column matrices such that $A u_{1}=\left(\begin{array}{l}1 \\ 0 \\ 0\end{array}\right)$ and $A u_{2}=\left(\begin{array}{l}0 \\ 1 \\ 0\end{array}\right)$, then $u_{1}+u_{2}$ is equal to
(A) $\left(\begin{array}{l}-1 \\ 1 \\ 0\end{array}\right)$
(B) $\left(\begin{array}{l}-1 \\ 1 \\ -0\end{array}\right)$
(C) $\left(\begin{array}{c}-1 \\ -1 \\ 0\end{array}\right)$
(D) $\left(\begin{array}{l}1 \\ -1 \\ -1\end{array}\right)$