You’d better ______ your flight reservation at the latest 3 days in advance.
When the group discussion is nearing its end, make sure to ____it with important points.
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.