Tom, clean up the broken glass _________ someone walks on it.
Once your business becomes international, ___ constantly will be part of your life.
I can hardly imagine such a little boy ___ across the Nile.
Jack, have you ____ your mid-term examination?
Faced with all the difficulties, the girl ____ her mother for comfort.
The International Maths Summer Camp was held in Wuhan,____ the top students in maths from all over the world.