________ you've got a chance, you might as well make full use of it.
We hope that she will ____ soon.
If we can keep ____ this speed, we'll arrive there in two or three hours.
The Great Wall was built to keep ____ the invaders.
I should very much like to have gone to the party, but______.
---Those shoes won't_____for mountain-climbing. ---_____this pair be OK?