--What do you think of Lady Gaga?--Maybe she is one of ________ singers in the world.
—What about playing football this afternoon, Sam? —I would rather at home than football. It’s too hot outside.
The cleaners make a great contribution to _____ the city clean.
He is a writer _____ a singer.
She was heard _____ an English song in her home last night.
Not only his parents but also his brother _____ to the Summer Palace. They haven’t been back.