Unitl tens of years ago, most zoos in such a way—animals in one area and birds in another.
There was only one ____ of transportation in this mountainous area five years ago.
He ____ the explosion, but no one else did. How lucky he was!
____ they did not believe him, what would they do then?
John shut everybody out of the kitchen ____ he could prepare his grand surprise for the party.
一Tell us, Mark ,what is the ____ of the American Civil War? 一 Well, is it because the black slaves wanted freedom?