『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 51 Passage 2阅读练习，TPO/Official 51 Passage 2原文答案解析，TPO/Official 51 Passage 2阅读原文练习音频翻译。

托福TPO/Official 51 Passage 2阅读原文题目答案及解析-新东方托福官方网校手机版

流体是一种物质，例如液体或气体，其中的成分粒子（通常是分子）可以相互移动。

A fluid is a substance, such as a liquid or gas, in which the component particles (usually molecules) can move past one another.

流体容易流动并符合其容器的形状。

Fluids flow easily and conform to the shape of their containers.

与流体在行星表面上运动有关的地质过程可以完全重塑行星表面很多次。

The geologic processes related to the movement of fluids on a planet’s surface can completely resurface a planet many times.

这些过程从太阳和行星本身的引力中获取能量。

These processes derive their energy from the Sun and the gravitational forces of the planet itself.

当这些流体与表面物质发生相互作用时，它们会移动粒子或与其发生化学反应，从而改性或产生物质。

As these fluids interact with surface materials, they move particles about or react chemically with them to modify or produce materials.

在一颗带有水圈的固体行星上，其行星表面和大气层之下或之上的水的质量总和中，只有很小一部分行星质量以表面流体的形式流动。

On a solid planet with a hydrosphere the combined mass of water on, under, or above a planet’s surface and an atmosphere, only a tiny fraction of the planetary mass flows as surface fluids.

然而，这些流体的运动可以极大地改变一颗行星。

Yet the movements of these fluids can drastically alter a planet.

以金星和地球为例，这两个都是有大气层的类地行星。

Consider Venus and Earth, both terrestrial planets with atmospheres.

金星和地球通常被视为双胞胎行星，但不是同卵双胞胎。

Venus and Earth are commonly regarded as twin planets but not identical twins.

它们的大小大致相同，由大致相同的物质混合物组成，并且一开始可能就被赋予了二氧化碳和水。

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.

然而，由于它们与太阳的距离不同，所以双胞胎的进化差异很大。

However, the twins evolved differently, largely because of differences in their distance from the Sun.

由于大量的内部热量，金星可能会继续进行有火山、裂谷和折叠的地质活动。

With a significant amount of internal heat, Venus may continue to be geologically active with volcanoes, rifting, and folding.

但是，它没有任何水文系统的迹象（水的流通和分布）：没有溪流，湖泊，海洋或冰川。

However, it lacks any sign of a hydrologic system (water circulation and distribution): there are no streams, lakes, oceans, or glaciers.

太空探测器表明，金星可能在初始阶段存在与地球一样多的水，但是它无法将其水保持液态。

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.

由于金星从太阳接收更多的热量，所以水从内部蒸发并上升到高层大气中，在那里太阳的紫外线将分子分解。

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.

大量释放的氢逃逸到太空，金星失去了水分。

Much of the freed hydrogen escaped into space, and Venus lost its water.

没有水，金星变得越来越不像地球，大气层中充满二氧化碳。

Without water, Venus became less and less like Earth and kept an atmosphere filled with carbon dioxide.

二氧化碳充当毯子，产生强烈的温室效应，使表面温度升高到足以熔化铅，并阻止碳酸盐矿物形成。

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.

火山不断向大气层中排放更多的二氧化碳。

Volcanoes continually vented more carbon dioxide into the atmosphere.

在地球上，从岩石风化到碳酸盐沉积岩的形成过程中，液态水从大气层中去除二氧化碳并将其与钙结合。

On Earth, liquid water removes carbon dioxide from the atmosphere and combines it with calcium, from rock weathering, to form carbonate sedimentary rocks.

如果没有液态水从大气层中去除碳，金星大气层中的二氧化碳含量仍然很高。

Without liquid water to remove carbon from the atmosphere, the level of carbon dioxide in the atmosphere of Venus remains high.

像金星一样，地球的大小足以使其具有地质活性，并使其重力场保持大气层。

Like Venus, Earth is large enough to be geologically active and for its gravitational field to hold an atmosphere.

与金星不同，地球与太阳的距离恰到好处，因此温度范围允许水以液体，固体和气体的形式存在。

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.

因此，水极易流动，并以连续的水文循环在整个地球上快速移动。

Water is thus extremely mobile and moves rapidly over the planet in a continuous hydrologic cycle.

在太阳的加热下，水以巨大的循环：从海洋流到大气层，流过河流系统的地貌，最终流回海洋。

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.

结果就是，地球的表面不断变化并侵蚀成细腻的河谷系统—和以撞击坑占主导地位的其他行星体的表面形成鲜明对比。

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.

地球上很少有流动水未触及的区域。

Few areas on Earth have been untouched by flowing water.

因此，河谷是其景观的主要特征。

As a result, river valleys are the dominant feature of its landscape.

同样，风力也会将细小的颗粒从大面积的区域刮走，并将它们沉积在由沙丘或黄土（细粒土壤沉积）组成的广袤沙海中。

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).

这些流体运动是由重力流系统引起的，这些重力流系统由来自太阳的热量供能。

These fluid movements are caused by gravity flow systems energized by heat from the Sun.

当大气层中的气体或水与地表的岩石反应形成具有不同性质的新化合物时，还会发生其他地质变化。

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.

这个过程的一个重要例子是：将地球大气层中大部分二氧化碳清除，从而形成碳酸盐岩。

An important example of this process was the removal of most of Earth’s carbon dioxide from its atmosphere to form carbonate rocks.

但是，如果地球离太阳稍微近一点，它的海洋就会蒸发。如果离太阳更远，海洋将结冰。

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.

由于液态水的存在，碳、氢和氧的自我复制分子在地球历史早期就发展出生命，并从根本上改变了地球的表面，使陆地的大部分地区被绿色植物覆盖。

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.

生命在这颗行星上蓬勃发展，并帮助创造了该行星的富氧和富氮大气层和适宜的温度。

Life thrives on this planet, and it helped create the planet’s oxygen and nitrogen-rich atmosphere and moderate temperatures.

The word “modify” in the passage is closest in meaning to

The word “drastically” in the passage is closest in meaning to

Paragraph 1 supports all of the following statements about fluids EXCEPT:

The word “prohibit” in the passage is closest in meaning to

According to paragraph 2, what is one difference between Earth and Venus?

It can be inferred from paragraph 2 that Earth evolved differently than Venus did in part because

According to paragraph 2, all of the following played a role in keeping carbon dioxide levels high in the atmosphere of Venus EXCEPT

The word “ultimately” in the passage is closest in meaning

According to paragraph 3, Earth’s surface is different from the surfaces of many other planetary bodies in which of the following ways?

According to paragraph 3, why is water able to move so freely on Earth?

Why does the author point out that on Earth “gases in chemical compounds”?

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.

Look at the four squares  that indicate where the following sentence could be added to the passage. Venus may not have always been this way.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.

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.

Surface Fluids on Venus and Earth 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 the combined mass of water on, under, or above a planet’s surface 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 Earth’s 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.