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推荐文章：大学英语四级模拟试题（十）
推荐文章简介：
Part II Reading Comprehension (35 minutes)Directions:There are four reading passages in this part. Each passage is followed by some questions. For each question there are four
1873, when it was accidentally discovered that the electrical resistance of the element selenium varied in proportion to the intensity of the light shining on it. Scientists quickly recognized that this provided a way of transforming light variations into
;electrical signals. Almost immediately a number of schemes were proposed for sending pictures by wire(it was, of course, before radio).
One of the earliest of these schemes was patterned on the human eye. Suggested by G. R. Carey in 1875, it envisioned a mosaic of selenium calls on which the picture to be transmitted would be focused by a lens system. At the receiving end there would be a similarly arranged mosaic made up of electric lights. Each selenium cell would be connected by an individual wire to the similarly placed light in the receiving mosaic. Light falling on the selenium cell would reproduce the original picture, had the necessary amplifiers and the right kind of lights been availablr, this system would have workrd. But it also would have required an imoractical number of connecting wires. Carey recognized this and in a second proposed to “scan” the cells-transmitting the signal from each cell to its associated light, in turn, over a single wire. If this were done fast enough, the retentive power of the eye would cause the resultant image to be&nb
sp;seen as a complete picture.
41. Which of the following is the best title for the passage?
A. Television in the Electronic Era
B. First Steps in the Invention of Television
C. The Art of Television
D. Harmful Effects of Television Viewing
正确答案是
42. In line 1, the word “being” could best be replaced by _____.
A. place
B. creature
C. subsistence
D. existence
正确答案是
43. An important discovery in earlyteleviosion was the electrical resistance of _____.
A. mosaics
B. the human eye
C. lenses
D. the element selenium
正确答案是
44. In 1875, Carey suggested that the human eye envisioned a mosaic of selenium cells on which the picture to be transmitted would be focused by ______.
A. wire
B. electric lights
C. a lens system
D. amplifiers
正确答案是
45. Following are the reasons why the first scheme for television was abandoned except _____.
A. he lacks an effective assistant
B. the necessary amplifers were unavailable
C. the proper lights were unavailable
D. the number of
;connecting wires is impractical
正确答案是
Questions 46-50 are based on the following passage.
Icebergs are among nature’s most spectacular creations, and yet most people have never seen one. A vague air of mystery envelops them. They come into being-somewhere-in faraway, line frigid waters, amid thunderous noise and splashing turbulence, which in most cases no one hears or sees. They exist only a short time and then slowly away just as unnoticed.
Objects of sheerest beauty, they have been called. Appearing in an endless variety of shapes, they may be dazzlingly white, or they may be glassy blue, green, or purple, tinted faintly or in darker hues. They are graceful, stately, inspiring-in calm, sunlit seas.
But they are also called frightening and dangerous, and that they are in the night, in the fog, and in storms. Even in clear weather one is wise to stay at a safe distance away from them. Most of their bilk is hidden below the visible top. Also, they may roll over unexpectedly, churning the waters around them.
Icebergs are parts&nbs
p;of glaciers that break off, drift into the water, float about a while, and finally melt. Iceberg afloat today are made of anowflakes that have fallen over long ages of time. They embody snows that drifted down hundreds, or many thousands, or in some cases maybe a million year ago. The snows fell in polar regions and on cold mountains, where they melted only a little or not at all, and so collected to great depths over the years and centuries.
As each year’s snow accumulation lay on the surface, evaporation and melting caused the snowflakes slowly fell on the top of the old, it too turned to icy grains. So blankets of snow and ice grains mounted layer upon layer and were of such great thickness that the weight&nb上一页 [1] [2] [3] [4] [5] [6] [7] [8] [9] 下一页 |
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