Mr. Irvine, who ________ in a high school for forty years, is now living in retirement.
Eye doctors recommend that a child’s first eye exam____ at the age of six months old.
______how others react to the book you have just read creates an added pleasure.
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.