21. The old paper mill has been ________ to make way for a new shopping centre.

　　A) held down B) kept down C) cut down D) turn down

　　22. It may be necessary to stop ________ in the learning process and go back to the difficult points in the lessons.

　　A) at a distance B) at intervals C) at case D) at length

　　23. You can hire a bicycle in many places. Usually you‘ll have to pay a ________.

　　A) deposit B) deal C) fare D) fond

　　24. My grandfather had always taken a ________ interest in my work， and I had an equal admiration for the stories of his time.

　　A) splendid B) weighty C) vague D) keen

　　25. ________ quantities of water are being used nowadays with the rapid development of industry and agriculture.

　　A) Excessive B) Extensive C) Extreme D) Exclusive

　　DBADA