You can not imagine the difficulty they had ____ the problem. It isn’t ____ easy.

The life in an American school is not the same __________ that in a Chinese school. They are different __________ each other.[ ]

I’m not going swimming this afternoon.— ______. I have to help my mother do some cleaning.

_________ did you do with old books?— I sent them to children in poor areas.

Do you want ______ computer games ?