It was not until the subprime loan crisis(次贷危机) ____ great damage to the American financial system that Americans ____ the severity of the situation.
He was so __________ a key university that he would work until late into the night.
-Look! Everything here is under construction. -Oh, has the building once _________ for exhibition been pulled down, too?
_________ the floor, I found his pen lying on the ground.
They urged that the library _________ open during the vacation.
Children under six are not __________to school except those of extraordinary intelligence.