—I think students should have mobile phones to call their parents.—_____. They often use them to play games instead.
He suddenly return ___ a stormy night.
__________! There comes a train!
The car runs ___ a very high speed and directly hits the tree beside the street.
The old man ___ a blue sweater is our new headmaster.
___ the beginning of the meeting, the president made a speech ___ how to reduce pollution.