33. Once ____, it can never ____.

A. see; forgotten B. see; forget

C. seen; be forgotten D. seeing; be forgotten

32. ____ to a high temperature, water will change into vapour.

A. Heated B. Heating C. Being heated D. Having heated

31. ____ their work, they had a rest.

A. Having finished B. Finished C. Having been finished D. Finishing

30. The story ____ by the famous writer is ____ at the factory now.

A. wrote, printed B. written, being printed

C. write, being printed D. written, printed

29. ____ from space, our earth, with water covering 70% of its surface, appears as a “blue planet.”

A. Seen B. Seeing C. Having seen D. To see

28. He had his leg ____ in the match yesterday.

A. to break B. break C. broken D. breaking

27. While ____ to foreigners, you must try your best to make yourself ____.

A. spoken; understood B. spoken; understand

C. speaking; understood D. speaking; understand

26. The building ____ will be a hospital.

A. build B. to be built C. being built D. being building

25. What made him ____?

A. frighten B. frightened C. frightening D. to frighten

24. Did you smell something ____.

A. burn B. burning C. to be burnt D. being burnt