公共英語考試閱讀精品
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文章一
American Black Bears
美國黑熊
American black bears appear in a variety of colors despite their name. In the eastern part of their range, most of these bears have shiny black fur, but in the west they grow brown, red, or even yellow coats. To the north, the black bear is actually gray or white in color. Even in the same litter, both brown and black furred bears may be born.Black bears are the smallest of all American bears, ranging in length from five to six feet, weighing from three hundred to five hundred pounds. Their eyes and ears are small and their eyesight and hearing are not as good as their sense of smell.
Like all bears, the black bear is timid, clumsy, and rarely dangerous, but if attacked, most can climb trees and cover ground at great speeds. When angry or frightened, it is a formidable enemy.Black bears feed on leaves, herbs, roots, fruit, berries, insects, fish, and even larger animals. One of the most interesting characteristics of bears, including the black bear, is their winter sleep. Unlike squirrels, woodchucks, and many other woodland animals, bears do not actually hibernate. Although the bear does not eat during the winter months,sustaining itself from body fat, its temperature remains almost normal, and it breathes regularly four or five times per minute.
Most black bears live alone, except during mating season. They prefer to live in caves, hollow logs, or dense thickets. A litter of one to four cubs is born in January or February after a gestation period of six to nine months, and they remain with their mother until they are fully grown or about one and a half years old. Black bears can live as long as thirty years in the wild, and even longer in game preserves set aside for them.
美國黑熊雖然被叫區域的東部,大部分黑 熊長有富有光澤的黑毛,但在西部,他們則長著棕色、紅色甚至是黃色的毛。
在北部,黑熊其實長著灰色或白色的毛。 就是在一胎所生的小熊中,都可能混雜棕毛和黑毛。 黑熊是 所有美洲熊中最小的,5~6 英尺長,300~500磅重。它們的眼睛和耳朵都很小,他們的視 力和聽覺不如嗅覺那樣好。 像所有的熊一樣,黑熊膽小,笨拙,很少具有危險性。 但如果受到攻擊,大部分黑熊會以很快的速度爬上樹和奔跑。 當發怒或受驚嚇時,黑熊會成為可 怕的對手。
黑熊以樹葉、草、樹根、水果、漿果、昆蟲、魚,甚至更大的動物為食。 熊類, 包括黑熊的最有趣的一個特點是他們的冬眠。與松鼠、旱獺和其它別的林地動物不同,熊 并不真正地冬眠。 雖然熊在冬天的幾個月中不吃東西,靠體內脂肪維持生命,但它們的體溫保持正常,并有規律地一分鐘呼吸 4 或 5 次。除交配季節外,大多數黑熊獨自生活。 他 們喜歡住在洞里、空心的大木頭里或茂密的樹叢里。 經過 6到 9 個月的懷孕期后一胎 1~4 個小熊在 1 月或 2 月出生。 它們同母熊住在一起,直到它們完全長大,即 1 歲半左右。黑熊在野外可以活到長達 30 年,在專門的保護區中甚至能活得更長。
文章二
Coal-fired Power Plants
火力發電廠
The invention of the incandescent light bulb by Thomas A. Edison in 1879 created a demand for a cheap, readily available fuel with which to generate large amounts of electric power. Coal seemed to fit the bill, and it fueled the earliest power stations (which were set up at the end of the nineteenth century by Edison himself). As more power plants were constructed throughout the country, the reliance on coal increased. Since the First World War, coal fired power plants have accounted for about half of the electricity produced in the United States each year. In 1986 such plants had a combined generating capacity of 289, 000 megawatts and consumed 83percent of the nearly 900 million tons of coal mined in the country that year. Given the uncertainty in the future growth of nuclear power and in the supply of oil and natural gas, coalfired power plants could well provide up to 70 percent of the electric power in the United States by the end of the century.
Yet, in spite of the fact that coal has long been a source of electricity and may remain one for many years (coal represents about 80 percent of United States fossil-fuel reserves), it has actually never been the most desirable fossil fuel for power plants. Coal contains less energy per unit of weight than natural gas or oil; it is difficult to transport, and it is associated with a host of environmental issues, among them acid rain. Since the late 1960’s problems of emission control and waste disposal have sharply reduced the appeal of coal-fired power plants. The cost of ameliorating these environmental problems along with the rising cost of building a facility as large and complex as a coal-fired power plant, have also made such plants less attractive from a purely economic perspective.
Changes in the technological base of coal-fired power plants could restore their attractiveness, however. Whereas some of these changes are evolutionary and are intended mainly to increase the productivity of existing plants, completely new technologies for burning coal cleanly are also being developed.
托馬斯.愛迪生1879年發明的白熾燈導致對便宜、易得、可生產大量電能的燃料的需求。
煤似乎符合這個要求,并成為第一批電廠的燃料(正是愛迪生本人在19世紀末建造了第一批電廠)。全國到處興建電廠時,對煤的依賴加深了。
自第一次世界大戰以來,美國每年約有一半的電力是以煤為燃料的電廠提供的。1986年這些電廠的總發電能力達到 28,900千瓦并且消耗了當年全國開采的九億噸煤的83%。 考慮到核能發展以及石 油、天然氣供應中的不確定因素,到本世紀末,火力發電廠仍可能為美國提供多達70%的電力。 然而,盡管煤長期以來一直是電力的原料之一并且可能會繼續如此(煤占美國化石燃 料儲量的 80%),它卻不是電廠的理想燃料。
煤的單位能量含量低于石油和天然氣,而且會導致包括酸雨在內的一系列環境問題。 從1960 年以來,排放控制和垃圾處理的問題極大地削弱了燃煤電廠的魅力。由于減輕這些環境問題需要大量資金,而且建造龐大復雜的燃煤 電廠的費用不斷上漲,也使得這些電廠從經濟角度上不具備吸引力。
改變火力發電廠的基礎技術卻可能恢復它們的吸引力。 雖然某些技術改進是漸進的,其目的只是提高現有電廠的生產率,但人們正在開發全新的清潔燃煤的技術。
文章三
Statistics
統計學
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 governmental units (state and statistics come from the same Latin root status) and a gentlemanly gambling father who relied on mathematics to increase his skill at playing the odds in games of chance.
The influence of the mother on the offspring, statistics, is represented by counting, measuring, describing, tabulating, ordering, and the taking of censuses --all of which led to modern descriptive statistics. From the influence of the father came modern inferential statistics, which is based squarely on theories of probability.
Descriptive statistics involves tabulating, depicting and describing collections of data. These data may be quantitative such as measures of height, intelligence or grade level --variables that are characterized by an underlying continuum --or the data may represent qualitative variables, such as sex, college major or personality type. Large masses of data must generally undergo a process of summarization or reduction before they are comprehensible. Descriptive statistics is a tool for describing or summarizing or reducing to comprehensible form the properties of an otherwise unwieldy mass of data.
Inferential statistics is a formalized body of methods for solving another class of problems that present great difficulties for the unaided human mind. This general class of problems characteristically involve attempts to make predictions using a sample of observations. For example, a school superintendent wishes to determine the proportion of children in a large school system who come to school without breakfast, have been vaccinated for flu, or whatever. Having a little knowledge of statistics, the superintendent would know that it is unnecessary and inefficient to question each child: the proportion for the entire district could be estimated fairly accurately from a sample of as few as 100 children. Thus, the purpose of inferential statistics is to predict or estimate characteristics of a population from a knowledge of the characteristics of only a sample of the population.
統計方法的早期發展受到兩種截然不同的影響。 統計學有一個"母親",她致力于井井有條地記錄政府機構的文件(國家和統計學這兩個詞源于同一個拉丁語詞根,status),還有一 個有紳士般的賭博"父親",他依靠數學來提高賭技,以便在幾率的游戲中取勝。 "母親"對其子女統計學的影響表現在計數、測量、描述、制表、歸類和人口普查。 所有這些導致了 現代描述統計學的誕生。
由于"父親"的影響則產生了完全基于概率論原理的現代推理統計 學。 描述統計學涉及對所收集數據的制表、制圖和描述。 這些數據可以是數量性的數據,如高度、智商、或者是層級性的數據--具有連續性的變量--或數據也可以代表性質變量,如 性別、大學專業或性格類型等等。
數量龐大的數據通常必須經過概括或刪減的程序才能為 人所理解。 描述統計學就是這樣一個工具,它對極其龐雜的數據進行描述、概括或刪減,使其變成能為人理解的東西。 推理統計學是一套已定形了的方法體系,它解決的是光憑人 腦極難解決的另一類問題。
這類問題的顯著特點是試圖通過取樣調查來作出預測。 例如, 有一位教育督察想知道在一個龐大的學校系統中,不吃早飯就上學的學生、已經做過防感冒免疫的學生,或其它任何類型的學生占多大比例。 若具備一些統計學的知識,這位督察應 明白,詢問每個孩子是沒有必要而且沒有效率的,只要用100 個孩子為樣本,他就可以相當 精確地得出這些孩子占整個學區的比例了。 因此,推理統計學的目的就是通過了解一個群體中一些樣本的特性,從而對整個群體的特性進行推測和估算。
文章四
Obtaining Fresh Water from Icebergs
從冰山中獲取淡水
The concept of obtaining fresh water from icebergs that are towed to populated areas and arid regions of the world was once treated as a joke more appropriate to cartoons than real life. But now it is being considered quite seriously by many nations, especially since scientists have warned that the human race will outgrow its fresh water supply faster than it runs out of food.Glaciers are a possible source of fresh water that has been overlooked until recently. Three-quarters of the Earth’s fresh water supply is still tied up in glacial ice, a reservoir of untapped fresh water so immense that it could sustain all the rivers of the world for 1,000 years. Floating on the oceans every year are 7,659 trillion metric tons of ice encased in 10,000 icebergs that break away from the polar ice caps, more than ninety percent of them from Antarctica.
Huge glaciers that stretch over the shallow continental shelf give birth to icebergs throughout the year. Icebergs are not like sea ice, which is formed when the sea itself freezes, rather, they are formed entirely on land, breaking off when glaciers spread over the sea. As they drift away from the polar region, icebergs sometimes move mysteriously in a direction opposite to the wind, pulled by subsurface currents. Because they melt more slowly than smaller pieces of ice, icebergs have been known to drift as far north as 35 degrees south of the equator in the Atlantic Ocean. To corral them and steer them to parts of the world where they are needed would not be too difficult.
The difficulty arises in other technical matters, such as the prevention of rapid melting in warmer climates and the funneling of fresh water to shore in great volume. But even if the icebergs lost half of their volume in towing, the water they could provide would be far cheaper than that produced by desalinization, or removing salt from water.
把冰山拖到世界上人口稠密的地區和干旱地帶,再從中獲取淡水,這個想法曾一度被認為是一個笑話,更適合于卡通畫,而非現實生活。然而現在,許多國家正相當認真地考慮 這件事情,特別是在科學家們發出警告之后。
科學家們認為人類將在耗盡糧食之前首先耗 盡淡水資源。冰川是一個直到最近以前一直被忽視的可能的淡水源。全球四分之三的淡水 還鎖在冰川的冰塊中。冰川就是一個蓄水池,其中未開發的淡水量是如此巨大,足夠支持全世界的江河 1000 年。 每年有 7,659 萬億公噸冰漂流在海洋中。它們包含在 10,000 座從極地冰帽中斷裂出來的冰山中。 這些冰山的 90%以上來自南極。 一年四季里,覆蓋在淺層大陸架上的巨大冰川生成了眾多冰山。 冰山和海水的冰不同,后者是海水自身結冰 形成的,而冰山則完全是在陸地上形成的。
當冰川伸展到海水中時,冰山就斷裂下來。 當漂離極地地區時,冰山有時會在底層洋流的推動下頗為神秘地逆風移動。由于冰山比小塊的冰融化要慢,因此有的冰山在大西洋中向北飄到了赤道以南 35°的地方。 把冰山蓄攔起 來并拖到世界上需要它們的地方將不會太困難。有困難的是其它的技術事宜。 比如,如何 防止冰山在較暖的氣候中迅速融化以及如何把大量的淡水收集到岸上去。 但是,即便在拖的過程中冰山失去了一半體積,這樣做也遠比從海水中脫鹽取得淡水便宜。
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