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阅读下面的短文，文中有15处空白，每处空白给出4个选项，请根据短文的内容从4个选项中选择1个最佳答案。 One of the most important technological developments during the 1980s has been the emergence of optical fiber communication as a major international industry. One indication of the (51) of this development is the total (52) of installed fiber, which was estimated to be 3.2 million kilometers in the U.S. alone by the end of 1987. Over 90% of this fiber was placed. (53) during the time period of 1982—1987. Long-haul trunk installations(长途干线设施) have dominated, (54) for about 95% of the fiber in the U.S. In the early 1950s the researchers who produced the first clad glass optical fibers were not (55) of using them. for communications. (56) , fiber optics was already a well-established commercial technology when the famous paper by Kao and Hockham, (57) the use of low-loss optical fibers for communication, appeared in 1966. The first low-loss silica fiber was described in a publication which appeared in October of 1970. The date of this publication is sometimes (58) as the beginning of the era of fiber communication. Although this development did receive (59) attention in the research community at- the time, it was far from inevitable that a major industry would evolve. The technological barriers appeared (60) because there were serious doubts as to (61) these fiber components could ever be produced economically enough, but the market potential was very significant. (62) , research and development activity expanded rapidly, and a number of important issues were (63) during the early 1970s. During the middle and late 1970s, the rate of progress towards marketable products accelerated as the emphasis (64) from research to engineering. Fibers with losses approaching the Payleigh limit of 2 dB/km at a wavelength of 0.8um were produced. By 1980 improvement in component performance, cost, and reliability led to major commitments (65) the part of telephone companies.
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下面有3篇短文，每篇短文后有5道题，每题后面有4个选项。请仔细阅读短文并根据短文回答其后面的问题，从4个选项中选择1个最佳答案。 第一篇 One of the greatest mysteries of the world, for ’which scientist have so far been unable to find any satisfactory explanation, is the Bermuda Triangle, sometime called "the Graveyard of the Atlantic." This is an area of the western Atlantic between Bermuda and Florida, roughly triangular in shape where since 1945 at least a hundred ships and planes and over a thousand people have disappeared. No wreckage had been found, no bodies, lifebelts or any other evidence of disater. It is as if these planes, ships and people had never existed. In some cases a routine radio message has been received from aircraft reporting everything in order a few minutes before all contact was lost, in others a weak S. O. S message has been picked up and, in perfect weather, inexplicable references to fog and loss of bearings. In the extraordinary case of five U. $. navy planes disappearing on a routine mission from Florida, the rescue place sent to locate them vanished also. There have been references to the curious white light or haze which is a feature of the sea in part of this area, and it is interesting to note that not only was this light, or streaks of light, observed by the astronauts on their way to space, but was also noted by Columbus, five centuries ago. Whether this light has any connection with the mysterious disappearance is unknown-it is just another curious circumstance as yet unexplained. Many theories, some bordering on the fantastic, have been advanced to account for the disturbing incidents that occur in the area of the Bermuda Triangle. It has been asked whether these disappearances are caused by extraterrestrial activity, by some undiscovered source of energy, or some dimension of time or space unguessed at by Man. This is no answer and speculation continues as anxiety increases. Before contact with missing aircraft has been last______.
简答题 分析南斯拉夫走上自治道路的原因。
阅读下面这篇短文，短文后列出7个句子，请根据短文的内容对每个句子做出判断。如果该句提供的是正确信息，请选择A；如果该句提供的是错误信息，请选择B；如果该句的信息文章中没有提及，请选择C。 Even plants can run a fever, especially when they’ re under attack by insects or disease. But unlike humans, plants can have their temperature taken from 3,000 feet away—straight up. A decade ago, adapting the infrared(红外线) scanning technology developed for military purposes and other satellites, physicist Stephen Paley came up with a quick way to take the temperature of crops to determine which ones are under stress. The goal was to let farmers precisely target pesticide(杀虫剂) spraying rather than rain poison on a whole field, which invariably includes plants that don’t have pest(害虫) problems. Even better, Paley’s Remote Scanning Services Company could detect crop problems before they became visible to the eye. Mounted on a plane flown at 3,000 feet at night, an infrared scanner measured the heat emitted by crops. The data Were transformed into a color-coded map showing where plants were running "fevers". Farmers could then spot-spray, using 50 to 70 percent less pesticide than they otherwise would. The bad news is that Paley’ s company closed down in 1984, after only three years. Farmers resisted the new technology and long-term backers were hard to find. But with the renewed concern about pesticides on produce, and refinements in infrared scanning, Paley hopes to get back into operation. Agriculture experts have no doubt the technology works. "This technique can be used on 75 percent of agricultural land in the United States," says George Oerther of Texas A&M. Ray Jackson, who recently retired from the Department of Agriculture, thinks remote infrared crop scanning could be adopted by the end of the decade. But only if Paley finds the financial backing which he failed to obtain 10 years ago. Infrared scanning will be used to estimate the damage to the crops in the near future.
有的人在理解诉讼时效制度时认为：“诉讼时效帮助了债务人逃债。”试用诉讼时效的有关知识对这种认定加以辨析。
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