15. An awful crash between an express train and a bus _____ , however, occur the other day in Russia.A. does B. did D. has to D. had to
If we leave right away,____ we’ll arrive on time.
The children,____ had played the whole day long, were worn out.
As the world’s population continues to grow, the ___of food becomes more and more of a concern.
Imyself more-it was a perfect day.
Mary worked here as a ____ secretary and ended up getting a full-time job with the company.