It was the third time that he of the changes of the meeting. [ ]

Carbondioxide from burning fuels is the most common ofthe so-called greenhouse gases. A．produced B．producing C．to be produced D．havingbeen produced

Andy is content with the toy. It is he has ever got.

It is difficult for any of us to eat better, exercise more, and sleep enough, ________we knowwe should.

27. Now and then they would ______ our house and have a talk with us.