(年北京市西城区高三5月二模试题)31. A person who has never tasted bitter won’t know ______ sweet is.
I lost my favourite pen, ______ I wrote my diary.
—Remember the first time we met, Jack? — Of course I do. You ______ in the library.
-I plan to invite our friends to have supper. -______We haven’t seen them such a long time.
The couple work in their garden every morning, ______ for a weight loss.
— Is there a flight to London this evening? — There ______be. I’ll phone the airport and find it out.