13.(　 ) Friendship is like money: easier made than ______. (03’北京)

　　 A. kept　　　　　 B. to be kept　　 C. keeping　　　　 D. having kept

12.(　 ) Unless ________ to speak, you should remain silent at the conference.(03’上海春)

　　 A. invited　　　　 B. inviting　　　 C. being invited　　 D. having invited

11.(　 ) Don’t use words, expressions, or phrases ________ only to people with specific knowledge. (02’上海)

　　 A. being known　　 B. having been known　　 C. to be known　 D. known

10.(　 ) Prices of daily goods ________ through a computer can be lower than store prices.(02’京皖春)

　　 A. are bought　　　 B. bought　　　 C. been bought　　 D. buying

9.(　 ) When ________, the museum will be open to the public next year. (02’上海春)

　　 A. completed　　　 B. completing　　　　 C. being completed　 D. to be completed

8.(　 ) ________ in 1636, Harvard is one of the most famous universities in the United States.(00’上海)

　　 A. Being founded　 B. It was founded　　 C. Founded　　 D. Founding

7.(　 ) The researcher is so designed that once ________ nothing can be done to change it.(02’全国)　 A. begins　　　　　　 B. having begun D. beginning　　 D. begun

6.(　 ) _______ such heavy pollution already, it may now be too late to clean up the river. (01’全国夏)

　　 A. Having suffered　　 B. Suffering　 C. To suffer　　　 D. Suffered

5.(　 ) _______ the general state of his health, it may take him a while to recover from the operation.(00’全国春)

4.(　 ) ________ is thought, he almost ran into the car in front of him.(96’全国)

　　 A. Losing　　　 B. Having lost　　　 C. Lost　　　　　 D. To lose