21、It was in the Ming Dynasty __________ the Great Wall was rebuilt to keep out northern tribes _________ threatened the Chinese heartland.

    A．that; that              B．that; where         C．when; that         D．when; when

20、It was in the Ming Dynasty __________ the Great Wall was rebuilt to keep out northern tribes _________ threatened the Chinese heartland.

    A．that; that              B．that; where         C．when; that         D．when; when

19、It was in the Ming Dynasty __________ the Great Wall was rebuilt to keep out northern tribes _________ threatened the Chinese heartland.

    A．that; that              B．that; where         C．when; that         D．when; when

18、It was in the Ming Dynasty __________ the Great Wall was rebuilt to keep out northern tribes _________ threatened the Chinese heartland.

    A．that; that              B．that; where         C．when; that         D．when; when

17、_________ is known to us all is that the old scientist, for ___________ life was hard in the past, still works very hard in his eighties.

    A．As; whom          B．What; whom      C．As; whose         D．What; whose

16、_________ she was sick, I was expected to take her place greatly surprised me, for I didn’t have much work experience.

    A．That if                 B．If                       C．If that              D．That

15、_________ working hard, he could get enough money ________.

    A．With; to live on      B．As; to live on         C．By; to live on      D．By, to live

14、Not all the holiday makers like lying on the _______ enjoying the sunbath.

    A．coast                   B．shore                 C．beach               D．waterfall

13、

With working mothers _______ , many families are finding they simply don’t have the time or energy to have more than one child.

    A．to increase           B．increased           C．are increasing            D．increasing

12、If you made ________ most of the _______, there would be _______ rise in production.

    A．the; equipments, a                                  B．a; equipment; a

    C．the; equipment, the                                 D．the, equipment; a