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OFFICIAL51 Directions: An introductory sentence for a brief summary of the passage is provided below Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points. Over time, the movement of surface fluids has greatly changed Venus and Earth.

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Surface Fluids on Venus and Earth
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A fluid is a substance, such as a liquid or gas, in which the component particles (usually molecules) can move past one another. Fluids flow easily and conform to the shape of their containers. The geologic processes related to the movement of fluids on a planet's surface can completely resurface a planet many times. These processes derive their energy from the Sun and the gravitational forces of the planet itself. As these fluids interact with surface materials, they move particles about or react chemically with them to modify or produce materials. On a solid planet with a hydrosphere and an atmosphere, only a tiny fraction of the planetary mass flows as surface fluids. Yet the movements of these fluids can drastically alter a planet. Consider Venus and Earth, both terrestrial planets with atmospheres.

Venus and Earth are commonly regarded as twin planets but not identical twins. They are about the same size, are composed of roughly the same mix of materials, and may have been comparably endowed at their beginning with carbon dioxide and water. However, the twins evolved differently largely because of differences in their distance from the Sun. With a significant amount of internal heat, Venus may continue to be geologically active with volcanoes, rifting, and folding. However, it lacks any sign of a hydrologic system (water circulation and distribution): there are no streams, lakes oceans or glaciers. Space probes suggest that Venus may have started with as much water as Earth, but it was unable to keep its water in liquid form. Because Venus receives more heat from the Sun, water released from the interior evaporated and rose to the upper atmosphere where the Sun's ultraviolet rays broke the molecules apart. Much of the freed hydrogen escaped into space, and Venus lost its water. Without water, Venus became less and less like Earth and kept an atmosphere filled with carbon dioxide. The carbon dioxide acts as a blanket, creating an intense greenhouse effect and driving surface temperatures high enough to melt lead and to prohibit the formation of carbonate minerals. Volcanoes continually vented more carbon dioxide into the atmosphere. On Earth, liquid water removes carbon dioxide from the atmosphere and combines it with calcium, from rock weathering, to form carbonate sedimentary rocks. Without liquid water to remove carbon from the atmosphere, the level of carbon dioxide in the atmosphere of Venus remains high.

Like Venus, Earth is large enough to be geologically active and for its gravitational field to hold an atmosphere. Unlike Venus, it is just the right distance from the Sun so that temperature ranges allow water to exist as a liquid, a solid, and a gas. Water is thus extremely mobile and moves rapidly over the planet in a continuous hydrologic cycle. Heated by the Sun, the water moves in great cycles from the oceans to the atmosphere, over the landscape in river systems, and ultimately back to the oceans. As a result, Earth's surface has been continually changed and eroded into delicate systems of river valleys - a remarkable contrast to the surfaces of other planetary bodies where impact craters dominate. Few areas on Earth have been untouched by flowing water. As a result, river valleys are the dominant feature of its landscape. Similarly, wind action has scoured fine particles away from large areas, depositing them elsewhere as vast sand seas dominated by dunes or in sheets of loess (fine-grained soil deposits). These fluid movements are caused by gravity flow systems energized by heat from the Sun. Other geologic changes occur when the gases in the atmosphere or water react with rocks at the surface to form new chemical compounds with different properties. An important example of this process was the removal of most of Earths carbon dioxide from its atmosphere to form carbonate rocks. However, if Earth were a little closer to the Sun, its oceans would evaporate; if it were farther from the Sun, the oceans would freeze solid. Because liquid water was present, self-replicating molecules of carbon, hydrogen, and oxygen developed life early in Earth's history and have radically modified its surface, blanketing huge parts of the continents with greenery. Life thrives on this planet, and it helped create the planet's oxygen- and nitrogen-rich atmosphere and moderate temperatures.

14.Directions: An introductory sentence for a brief summary of the passage is provided below Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points. Over time, the movement of surface fluids has greatly changed Venus and Earth.

A.Although Venus is about the same size as Earth, its greater volcanic activity has added considerably to carbon dioxide levels in its atmosphere.

B.Like Venus Earth has an atmosphere, but Earth's atmosphere has far more oxygen and nitrogen than does the atmosphere of Venus.

C.On Earth, chemical reactions involving fluids remove carbon dioxide from the atmosphere by giving rise to carbonate rocks, and winds energized by gravity flow systems move fine particles from one place to another. 

D.Because Venus lost the water it originally had, most of its carbon dioxide remained in its atmosphere, causing the planet to become very warm.

E.On Earth, the dominance of river valley landscapes and the existence of life are due to the planet s hydrologic cycle.

F.The evaporation of liquid water from Earth's surface is largely limited by the life forms that have developed, particularly the vegetation.

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正确答案:CDE
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【题目翻译】说明:下面提供一篇短文摘要的介绍性句子,通过选择三个答案来完成摘要,这些答案表达了短文中最重要的观点。有些句子不属于摘要,因为它们表达了文章中没有呈现的想法,或者是文章中的次要思想。 随着时间的推移,表面流体的运动已经极大地改变了金星和地球。 A:虽然金星的大小和地球差不多,但是它更大的火山活动大大增加了大气中的二氧化碳含量。 B:就像金星一样,地球也有大气层,但是地球大气层的氧气和氮气要比金星大气层多得多。 C:在地球上,涉及流体的化学反应通过产生碳酸盐岩从大气中除去二氧化碳,由重力流系统激发的风将细颗粒从一个地方移动到另一个地方。 D:因为金星失去了原来拥有的水,所以大部分的二氧化碳留在大气中,导致地球变得非常温暖。 E:在地球上,河谷景观和生命存在的主导地位是地球水文循环的结果。 F:液态水从地球表面的蒸发在很大程度上受限于已经形成的生命形式,尤其是植被。 【判定题型】:根据问题的提问方式和6选3的作答方式可以确定该题目为概要小结题。 【选项定位及分析】 A选项:虽然金星和地球一样大,它更频繁的火山活动增加了其大气层中二氧化碳的含量。A选项对应文章第二段,但是A选项有2点错误。1是文章并没有提到金星火山活动比地球更频繁;2是A选项是一处细节描写,不是文章主干。故A选项排除。 B选项:像金星一样,地球也含有大气层,但地球的大气层含有更多氧气和氮气。这句话带有误导性,文章从未提及“地球的大气层含有更多的氧气和氮气”这一信息,仅在文末说道:“Life thrives on this planet, and it helped create the planet’s oxygen - and nitrogen-rich atmosphere and moderate temperatures.”这句话只是在表达地球上有丰富的氧气与氮气而已,根本没有比较过金星和地球的氮氧含量,故该选项信息错误(而且气体含量的高低也不是这篇文章的主干信息),故B选项排除。 C选项:在地球上,液体从大气层中除去二氧化碳,形成碳酸盐岩,而由重力流系统驱使的风力作用将细颗粒带到其他地区。对应文章第三段内容,C选项概述了2种流体作用改变地貌的方式,符合文意,正确。 D选项:因为金星失去了原有的水,二氧化碳一直存在于大气中,导致了温室效应。对应文章第二段内容,符合文意,正确。 E选项:在地球上,河谷地貌和生命是由地球的水文圈造成的。E选项对应文章倒数第二句“Because liquid water was present, self-replicating molecules of carbon, hydrogen, and oxygen developed life early in Earth's history and have radically modified its surface, blanketing huge parts of the continents with greenery.” 选项内容是正确的,且也属于主干信息,故为正确选项。 F选项:从地球表面蒸发的液态水,很大程度上受到生命形式的限制。该信息在全文中并未提及,故排除。

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