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案例分析题关系数据库是（）的集合，它由一个或多个关系模式定义。关系数据库的规范化理论指出：关系数据库中的关系应满足一定的要求，最起码的要求是达到1NF，即满足（）。因此，通常情况下，（）不可以作为关系数据库的关系。 关系数据库的规范化理论指出：关系数据库中的关系应满足一定的要求，最起码的要求是达到1NF，即满足（）。
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已知某显示器的分辨率为1024×768，那么用它浏览一幅分辨率为500×400的图．像时，下列说法正确的是 (54) 。
Some pessimistic experts feel that the automobile is bound to fall into disuse. They see a day in the not-mo-distant future when all autos will be abandoned and allowed to rust. Other authorities, however, think the auto is here to stay. They hold that the car will remain a leading means of travel in the foreseeable future. The motorcar will undoubtedly change significantly over the next 30 years. It should become smaller, safer, and more economical, and should not be powered by the gasoline engine. The car of the future should be far more pollution-free than present types. Regardless of its power source, the auto in the future will still be the main problem in urban traffic congestion (拥挤). One proposed solution to this problem is the automated highway system. When the auto enters the highway system, a retractable (可伸缩的) arm will drop from the auto and make contact with a rail, which is similar to those powering subway trains electrically. Once attached to the rail, the car will become electrically powered from the system, and control of the vehicle will pass to a central computer. The computer will then monitor all of the car’s movements. The driver will use a telephone to dial instructions about his destination into the system. The computer will calculate the best route, and reserve space for the car all the way to the correct exit from the highway. The driver will then be free to relax and wak for the buzzer (蜂鸣器) that will warn of his coming exit. It is estimated that an automated highway will be able to handle 10,000 vehicles per hour, compared with the 1,400 to 2,000 vehicles that can be carried by a present-day highway. What is the author’s main concern
There seems never to have been a civilization without toys, but when and how they developed is unknown. They probably came about just to five children something to do. In the ancient world, as is today, most boys played with some kinds of toys and most girls with another. In societies where social roles are rigidly determined, boys pattern their play after the activities of their fathers and girls after the tasks o~ their mothers. This is true because boys and girls are being prepared, even in play, to step into the roles and responsibilities of the adult world. What is remarkable about the history of toys is not so much how they changed over the centuries but how much they have remained the same. The changes have been mostly in terms of craftsmanship, mechanics, and technology. It is the universality of toys with regard to their development in all part of the world and their persistence to the present that is amazing. In Egypt, the Americas, China, Japan and among the Arctic (北极的) peoples, generally the same kinds of toys appeared. Variations depended on local customs and ways of life because toys imitate their surroundings. Nearly every civilization had dolls, little weapons, toy soldiers, tiny animals and vehicles. Because toys can be generally regarded as a kind of art form, they have not been subject to technological leaps that characterize inventions for adult use. The progress from the wheel to the oxcart to the automobile is a direct line of ascent (进步). The progress from a rattle (拨浪鼓) used by a baby in 3000 B.C. to one used by an infant today, however, is not characterized by inventiveness. Each rattle is the product of the artistic tastes of the times and subject to the limitations of available materials. Which of the following is the author’s view on the historical development of toys
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