1. If the complex numbers $a, b, c$ are distinct, and the points they correspond to are $A, B, C, \omega=-\frac{1}{2}+\frac{\sqrt{3}}{2} \mathrm{i}$, and $a+\omega b+ \omega^{2} c=0$, then $\triangle A B C$ is
A. Right triangle
B. Obtuse triangle
C. Equilateral triangle
D. Isosceles right triangle
1. C $(a-c)+(b-c) \omega=0, a-c=\left(\cos 120^{\circ}+\mathrm{i} \sin 120^{\circ}\right)(c-b)$

Translates to:

1. C $(a-c)+(b-c) \omega=0, a-c=\left(\cos 120^{\circ}+\mathrm{i} \sin 120^{\circ}\right)(c-b)$