Great changes ______ in the past few years, and a lot of factories ________.
Our school has used computers in teaching for ten years. As a result, not only______, but students become more interested in their lessons.
I arrived home at midnight, _______ my parents had been waiting for nearly three hours.
--- It’s wrong of a student to follow ______ his teacher says. --- It’s true. I can’t agree ______.
The teacher set such a difficult problem ________none of us could solve.
If we want ______much cleaner world, we should reduce _______ emission of carbon dioxide.