------- Alice, why didn’t you come yesterday? ------- I _______, but I had an unexpected visitor.
When you read the book, you’d better make a mark _____ you have any questions.
You should let your children play ______ you can see them.
Now he works in the factory ______ his father used to work.
The visitor asked to have his picture taken _______ stood the famous tower.
They kept trying _____ they must have known it was hopeless.