—She fly. But plane tickets are very expensive this time of year.
A:may
B:has to
C:need
D:must
我经常听摇滚乐。
I often listen to____ ____
绕地球做匀速圆周运动的人造卫星,轨道半径越大的卫星,它的( )
下列各项中语意明确,没有语病的一项是( )