The theory of plate tectonics describes the motions of the lithosphere, the comparatively rigid outer layer of the Earth that includes all the crust and part of the underlying mantle. The lithosphere(n.[地]岩石圈)is divided into a few dozen plates o

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An important new industry, oil refining, grew after the Civil war. Crude oil, or petroleum a dark, thick ooze from the earth had been known for hundreds of years, but little use had ever been made of it. In the 1850s Samuel M. Kier, a manufacturer i

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38 Topaz Topaz is a hard, transparent mineral. It is a compound of aluminum, silica, and fluorine. Gem topaz is valuable. Jewelers call this variety of the stone precious topaz. The best-known precious topaz gems range in color from rich yellow to l

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37 Icebergs Icebergs are among natures 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, frigid waters, amid thunderous noise and splashi

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34 Raising Oysters In the oysters were raised in much the same way as dirt farmers raised tomatoes- by transplanting them. First, farmers selected the oyster bed, cleared the bottom of old shells and other debris, then scattered clean shells about.

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31 British Columbia British Columbia is the third largest Canadian provinces, both in area and population. It is nearly 1.5 times as large as Texas, and extends 800 miles(1,280km) north from the United States border. It includes Canadas entire west

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27. Scientific Theories In science, a theory is a reasonable explanation of observed events that are related. A theory often involves an imaginary model that helps scientists picture the way an observed event could be produced. A good example of thi

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30 The origin of Refrigerators By the mid-nineteenth century, the term icebox had entered the American language, but ice was still only beginning to affect the diet of ordinary citizens in the United States. The ice trade grew with the growth of cit

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33 Plankton浮游生物. Scattered through the seas of the world are billions of tons of small plants and animals called plankton. Most of these plants and animals are too small for the human eye to see. They drift about lazily with the currents, provid

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32 Botany Botany, the study of plants, occupies a peculiar position in the history of human knowledge. For many thousands of years it was the one field of awareness about which humans had anything more than the vaguest of insights. It is impossible

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29 Telecommuting Telecommuting-- substituting the computer for the trip to the job ----has been hailed as a solution to all kinds of problems related to office work. For workers it promises freedom from the office, less time wasted in traffic, and h

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25. Movie Music Accustomed though we are to speaking of the films made before 1927 as silent, the film has never been, in the full sense of the word, silent. From the very beginning, music was regarded as an indispensable accompaniment; when the Lum

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26. International Business and Cross-cultural Communication The increase in international business and in foreign investment has created a need for executives with knowledge of foreign languages and skills in cross-cultural communication. Americans,

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Although Henry Fords name is closely associated with the concept of mass production, he should receive equal credit for introducing labor practices as early as 1913 that would be considered advanced even by todays standards. Safety measures were imp

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20 The Historical Significance of American Revolution The ways of history are so intricate and the motivations of human actions so complex that it is always hazardous to attempt to represent events covering a number of years, a multiplicity of perso

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22 Collectibles Collectibles have been a part of almost every culture since ancient times. Whereas some objects have been collected for their usefulness, others have been selected for their aesthetic beauty alone. In the United States, the kinds of

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21 The Origin of Sports When did sport begin? If sport is, in essence, play, the claim might be made that sport is much older than humankind, for , as we all have observed, the beasts play. Dogs and cats wrestle and play ball games. Fishes and birds

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19 childrens numerical skills people appear to born to compute. The numerical skills of children develop so early and so inexorably that it is easy to imagine an internal clock of mathematical maturity guiding their growth. Not long after learning t

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18.Modern American Universities Before the 1850s, the United States had a number of small colleges, most of them dating from colonial days. They were small, church connected institutions whose primary concern was to shape the moral character of thei

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43.Statistics There were two widely divergent influences on the early development of statistical methods. Statistics had a mother who was dedicated to keeping orderly records of government units (states and statistics come from the same Latin root s

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