直线 $x \cos \alpha+\sqrt{3} y+2=0$ 的倾斜角的范围是
A. $\left[0, \frac{\pi}{6}\right] \bigcup\left[\frac{5 \pi}{6}, \pi\right)$
B. $\left[0, \frac{5 \pi}{6}\right]$
C. $\left[\frac{\pi}{6}, \frac{\pi}{2}\right) \cup\left(\frac{\pi}{2}, \frac{5 \pi}{6}\right]$
D. $\left[\frac{\pi}{6}, \frac{5 \pi}{6}\right]$