A:They are going to come up with a good idea
B:They are going to wake up Bob.
C:They are going to make Bob happier.
被称为世界“雨极”的地方是( )
如图所示的四种现象中,由于光的折射形成的是( )
已知:关于x的方程x2﹣3x+2k﹣1=0有两个实数根.