He wrote a letter________he explained what had happened in the accident.
21. Perseverance is a kind of quality, and that’s ______ it takes to do anything well.
20. —Why was __ you lost all your keys?—It was because of my carelessness.
19. To work at home has been made _____ with the development of the Internet.
18. ------- Could you please tell me more about the city? ------- Sorry, I’m a newcomer. I know nothing else ______ you know now.
17. ________ is expected, according to the on-line survey, is that prices of houses will not go up any longer.