12. A team of engineer has been developing a space cleanup satellite to eliminate man-made orbital debris, ( ) broken-down satellites or tossed-away rocket stages.

67、As the director can't come to the reception, I'm representing the company ( ).

66、You must let me have the annual report without ( ) by ten o'clock tomorrow morning.

65、While he was in Beijing, he spent all his time ( ) some important museums and buildings.

64、The diversity of tropical plants in the region represents a seemingly ( ) source of raw materials, of which only a few have been utilized.

63、Rite of Passage is a good novel by any standards;( ), it should rank high on any list of science fiction.

62、In the present economic ( ) we can make even greater progress than previously.

61、We should make a clear ( ) between 'competent' and 'proficient' for the purposes of our discussion.

60、The chances of a repetition of those unfortunate events are ( ) indeed.

59、This project would ( ) a huge increase in defense spending.

58、In winter drivers have trouble stopping their cars from ( ) on icy roads.