“Only two centimeters higher, _______ break the world record,” encouraged the coach.
The research is so designed that once _____ nothing can be done to change it.
If _____ carefully, the experiment will be successful.
He is a man of few words, and seldom speaks until _____ to.
They kept trying _____ they must have known it was hopeless.
There are five pairs, but I'm at a loss which _____ to buy.