20. don’t leave the water ____ while you brush your teeth.

A. run　 B running　 C being run　 D to run

19. the flu is believed ____ by viruses that like to reproduce in the cells inside the human nose and throat.

A.　　 causing　 B being caused　 C to be caused　 D be have caused

18. my adviser encouraged ____ a summer course to improve my writing skills.

A. for me taking　 B me taking　 C for me to take　 D me to take

17. the disc, digitally ____ in the studio, sounded fantastic at the party that night.

A. recorded　 B recording　 C to be recorded　 D having recorded

16. the flowers ____ sweet in the botanic garden attract the visitors to the beauty of nature.

A. to smell　 B smelling　　 C smell　 D to be smell

15. reading is an experience quite different from watching TV; there are pictures ___ in your mind instead of before your eyes.

A. to form　 B　 form　 C forming　 D having formed

14. you were silly not ___ your car.

A. to lock　 B. to have locked　 C locking　 D having locked

13. the news reporters hurried to the airport, only ____ the film stars had left.

A. to tell　 B to be told　 C. telling　 D told

12. Helen had to shout ____ above the sound of the music.

A.　　 making herself hear　 B to make herself hear

B.　　　 C making herself heard　 D to make herself heard’

11. the old man, ___ abroad for 20 years, is on the way back to his mother land.

A. to work　 B work　 C to have work　 D having work