–Where are the students? How could they keep us waiting for so long? –They started an hour ago and they ____ be here in fifteen minutes, I think.
You should make it a rule to leave things _________ you can find them again.
Now he works in the factory _________his father used to work.
You should let your children play _________ you can see them.
The school was built _________ there had once been a church.
—Mom, what did the doctor say? —He advised me to live _________ the air is fresher.