Everyone ______________ to their teacher in the classroom. [ ]

A. are listening

B. is listening

C. listened

D. listen

如图所示，是光从空气斜射入玻璃中时发生反射和折射的光路图，已知∠3=∠6，则入射光线是       ，界面是      ，界面的        边是玻璃。