Look out! Don’t get close to the house, ______ the roof is under repair.
In the USA, _______ Thanksgiving Day is a harvest festival. Traditionally, it is _______ time to give thanks for the harvest and express gratitude in general.
—It’s hard to believe that Jack ________ have fought with the policeman.—Yes. If one ________ ask for trouble, it can't be helped.
___ you lose the paper document, sign in www. Sina.com, __ you might download all you need.
When you read the book, you’d better make a mark _____ you have any questions.
The child tiptoed quietly to the bird. ______ into the forest when he was about to catch it.