6. The locus point such that lines drawn from it intersect the lines \( \frac{x+a}{0}=\frac{y}{\sin \alpha}=\frac{z}{-\cos \alpha} \) and \( \frac{x-a}{0}=\frac{y}{\sin \alpha}=\frac{z}{\cos \alpha} \) at equal angles is \( x y=\sqrt{3} a z \). Then \( \alpha \) can be
(A)) \( \frac{\pi}{3} \)
(B) \( \frac{2 \pi}{3} \)
(C) \( \frac{4 \pi}{3} \)
(D) \( \frac{5 \pi}{3} \)
