2. Given the sides of $\triangle A B C$ are $a, b, c$ and satisfy $a^{2}-a-2 b-2 c=0$, and $a+2 b-2 c+3=0$. Then the largest interior angle of $\triangle A B C$ is ( ).
(A) $150^{\circ}$
(B) $120^{\circ}$
(C) $90^{\circ}$
(D) $60^{\circ}$
2.B.

From the given conditions, we have
$$
\begin{array}{l}
a+2 b+2 c=a^{2}, a+2 b-2 c=-3 \\
\Rightarrow(a+2 b+2 c)(a+2 b-2 c)=-3 a^{2} \\
\Rightarrow(a+2 b)^{2}-4 c^{2}=-3 a^{2} \\
\Rightarrow c^{2}=a^{2}+b^{2}+a b \\
\Rightarrow \cos C=-\frac{1}{2} \Rightarrow \angle C=120^{\circ} .
\end{array}
$$