文勇的新托福黄金&ccedil

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Unformatted text preview: ivers, which cut through the rocks and carry away debris from the mountains to the lowlands. 6. Why does the author mention Carbon dioxide in the passage? ○To explain the origin of a chemical that can erode rocks ○To contrast carbon dioxide with carbonic acid ○To give an example of how rainwater penetrates soil ○To argue for the desirability of preventing erosion 7. The word eeps in the passage is closest in meaning to s ○Dries gradually ○Flows slowly ○Freezes quickly ○Warms slightly Paragraph 6: Under very cold conditions, rocks can be shattered by ice and frost. Glaciers may form in permanently cold areas, and these slowly moving masses of ice cut out valleys, carrying with them huge quantities of eroded rock debris. In dry areas the wind is the principal agent of erosion. It carries fine particles of sand, which bombard exposed rock surfaces, thereby wearing them into yet more sand. Even living things contribute to the formation of landscapes. Tree roots force their way into cracks in rocks and, in so doing, speed their splitting. In contrast, the roots of grasses and other small plants may help to hold loose soil fragments together, thereby helping to prevent erosion by the wind. 8. The word hem in the passage refers to t ○Cold areas ○Masses of ice ○Valleys ○Rock debris Paragraph 2: Hills and mountains are often regarded as the epitome of permanence, successfully resisting the destructive forces of nature, but in fact they tend to be relatively short­lived in geological terms. As a general rule, the higher a mountain is, the more recently it was formed; for example, the high mountains of the Himalayas are only about 50 million years old. Lower mountains tend to be older, and are often the eroded relics of much higher mountain chains. About 400 million years ago, when the present­day continents of North America and Europe were 84 Mail@liuwenyong.com 在在在在在在 www.liuwenyong.com 在在在在在在在在在在在在在在,在在在在在在在在在在 joined, the Caledonian mountain chain was the same size as the modern Himalayas. Today, however, the relics of the Caledonian orogeny (mountain­building period) exist as the comparatively low mountains of Greenland, the northern Appalachians in the United States, the Scottish Highlands, and the Norwegian coastal plateau. 9. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. ○When they are relatively young, hills and mountains successfully resist the destructive forces of nature. ○Although they seem permanent, hills and mountains exist for a relatively short period of geological time. ○Hills and mountains successfully resist the destructive forces of nature, but only for a short time. ○Hills and mountains resist the destructive forces of nature better than other types of landforms. Paragraph 6: Under very cold conditions, rocks can be shatter...
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