“When _____ he come?” “I don’t know, but when he _____, I’ll tell you.”
Scientists ______ thousands of chemicals before they decided on the right one in the end.
What Mr. White said sounds ______ .
It's obvious that the experiment ______ a great success.
To their great ______ , Tom's problem proved not to be as serious as they had feared.
______ we had read your letter ______ the true state of affairs.