His sister left home in 1998,and __________ since.
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.