A

\[\{0\}\]

B

\[\left\{ 0; \frac{2\pi}{3}; \frac{4\pi}{3} \right\}\]

C

\[\left\{ 0; \pi ; \frac{\pi}{4}\right\}\]

D

\[\{0;\pi \}\]

E

\[\left\{ 0; \frac{\pi}{2} ; \frac{\pi}{6}\right\}\]