已知 $A=\left(\begin{array}{lll}1 & 1 & 0 \\ 1 & 1 & 0 \\ 0 & 0 & 1\end{array}\right)$ ，那么下列矩阵 $\left(\begin{array}{ccc}1 & -1 & 0 \\ -1 & 1 & 0 \\ 0 & 0 & 1\end{array}\right),\left(\begin{array}{lll}3 & 0 & 0 \\ 0 & 2 & 0 \\ 0 & 0 & 0\end{array}\right),\left(\begin{array}{lll}1 & 2 & 1 \\ 2 & 5 & 2 \\ 1 & 2 & 1\end{array}\right)$ 中，与 $A$ 合同的矩阵有
A. 3 个．
B. 2 个．
C. 1 个．
D. 0 个．