The population of many Alaskan cities has ______ doubled in the past three years.
| A．as great as | B．as many as | C． more than | D．larger than |
The roads have ______ because of people’s dependence on cars.
| A．jammed | B．been jamming | C．to jam | D．been jammed |
Green organizations are trying to save rain forests that have been _____ by farmers.
| A．created | B．ruined | C．threatened | D．protected |
After dinner he gave Mr Richard ______ ride to ______ Great Wall.
| A．the; a | B．a; the | C．不填; a | D．不填; the |
______ I admit that all these problems are difficult, I don’t agree that they can’t be solved.
| A．Unless | B．While | C．Until | D．Since |
Clothing made of man-made fibers has certain advantages over _______ made of natural fibers like cotton, wool or silk.
| A．the ones | B．one | C．that | D．what |