A:7
B:6
C:5
D:4
A、On Monday she'll go to school.
B、It's a robot.
C、Yes , I will.
D、No , it won't.
E、Yes , they will.
先化简,再求值:xx2-1÷1+1x-1,其中x=3-1.
光斜射到平面镜上,入射光线与镜面的夹角为30°,反射角为( )