It was not until 1920 regular radio broadcast began.
| A．while | B．which | C．that | D．since |
Everyone here will thank the firefighter for the things they have done to prevent fires______ the environment safer.
| A．make | B．to making | C．to make | D．from making |
______ with so many challenges, Yang Guang, a blind young fellow, didn’t give up; he made great efforts to win success.
| A．Facing | B．To face | C．Faced | D．Face |
— Why do you look so worried?
—My computer broke down and my essay ______ unfinished since.
| A．had left | B．has been left | C．has left | D．was left |
By no means ______ true that all English people know their own language well.
| A．is that | B．that is | C．is it | D．it is |
Was it in 1969 ________ the American astronaut succeeded ________ landing on the moon?
| A．when；on | B．that；on | C．when；in | D．that；in |