设 $A$ 为 3 阶矩阵， $P$ 为 3 阶可逆矩阵，且
$$
P^{-1} A P=\left(\begin{array}{lll}
1 & 0 & 0 \\
0 & 1 & 0 \\
0 & 0 & 2
\end{array}\right),
$$
若 $P=\left(\alpha_1, \alpha_2, \alpha_3\right) ， Q=\left(\alpha_1+\alpha_2, \alpha_2, \alpha_3\right)$ ，则 $Q^{-1} A Q=$
A. $\left(\begin{array}{lll}1 & 0 & 0 \\ 0 & 2 & 0 \\ 0 & 0 & 1\end{array}\right)$
B. $\left(\begin{array}{lll}1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 2\end{array}\right)$
C. $\left(\begin{array}{lll}2 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 2\end{array}\right)$
D. $\left(\begin{array}{lll}2 & 0 & 0 \\ 0 & 2 & 0 \\ 0 & 0 & 1\end{array}\right)$