The real reason why prices ____ , and still are, too high is complex, and no short discussion can satisfactorily explain this problem.
Before the conference, a new problem came up __________ could speak on behalf of our group.
He dressed up and went to the party as if ___________.
Scientist are not sure about the ___________ of water on the Mars.
Don’t push me! __________ you know the truth right away?
. He __________ full marks, but he was so careless as to make a spelling mistake.