There is a popular opinion among teachers _____ reviewing the lesson after class can help students learn better.
“Where _______ go to work?” “Where _______ go to work is not known.”
It was when she was about to go to bed ______ the telephone rang.
None knows if _______ that boy, but if _______ him, her parents will be disappointed.
The problem is _____ has caused us a lot of trouble.
He pointed to ______ looked like a tomb and said, “Ghost.”