. —On the contrary, I think it is the mother, rather than her children, _________to blame. —I agree with you.
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.