2. If the three sides of $\triangle A B C$ are $a, b, c$ and satisfy
$$
a^{2}-a-2 b-2 c=0 \text { and } a+2 b-2 c+3=0 \text {, }
$$

then the degree of its largest interior angle is ( ).
(A) $150^{\circ}$
(B) $120^{\circ}$
(C) $90^{\circ}$
(D) $60^{\circ}$
2. (B).

From $(a+2 b+2 c)(a+2 b-2 c)=-3 a^{2}$,
we have $a^{2}+b^{2}+a b=c^{2}$, thus $\cos C=-\frac{1}{2}$.