It is a teacher's responsibility always to hope, ________ with learning, a boy's character might be changed.
Don’t have the lights ______ all day long. It is a waste of electricity.
Either you or the headmaster ______ the prizes to the gifted students.
The 2010 Shanghai World Expo is well worth ______.
I am interested in traveling. It is ______ but ______.
The windows haven’t cleaned for a long time. They need ______.