托福阅读备考之天文学习题

　　在托福考试中，天文学科也从来都是被重点考察的学科之一。今天就来跟大家分享两道托福TPO模考软件中天文学的阅读题目。

　　第一道题目来自于TPO 8 Running Water on Mars

　　Paragraph 2: Outflow channels are probably relics of catastrophic flooding on Mars long ago. They appear only in equatorial regions and generally do not form extensive interconnected networks. Instead, they are probably the paths taken by huge volumes of water draining from the southern highlands into the northern plains. The onrushing water arising from these flash floods likely also formed the odd teardrop-shaped “islands” (resembling the miniature versions seen in the wet sand of our beaches at low tide) that have been found on the plains close to the ends of the outflow channels. Judging from the width and depth of the channels, the flow rates must have been truly enormous-perhaps as much as a hundred times greater than the 105 tons per second carried by the great Amazon river. Flooding shaped the outflow channels approximately 3 billion years ago, about the same times as the northern volcanic plains formed.

　　Question: According to paragraph 2, all of the following are true of the outflow channels on Mars EXCEPT:

　　A. They formed at around the same time that volcanic activity was occurring on the northern plains.

　　B. They are found only on certain parts of the Martian surface.

　　C. They sometimes empty onto what appear to have once been the wet sands of tidal beaches.

　　D. They are thought to have carried water northward from the equatorial regions.

　　解析：题干问的是原文关于“outflow channels”的描述。在真正考试中，把原文阅读完毕再去和选项比较会花费较多时间。因此，比较合理的做题顺序是，先读选项，然后拿选项和原文信息去比对。

　　A选项说的是outflow channel的形成时间和火山活动在北部平原的发生时间是相同的。快速浏览原文，只有在最后一句提到了它们的形成时间，说大概在30亿年前，about引导的时间状语很重要，补充说明了这一时间和北部火山平原形成的时间相同。A正确。

　　B选项说的是火山形成的地点，只在火星表面的特定区域。看原文，第二句，说的是它们只在赤道区域出现。B也正确。

　　C选项说的是它们有时候会流到曾经的湿沙地上。原文在提到tidal beaches时，并没有提到这一信息，因此，C选项是不符合原文的。

　　D选项说的是河水从赤道（南）向北流动。和原文第三句话吻合：这些河流的走向是从南部高低到北部平原。

　　因此，本题的正确答案为C项。

　　第二道题目来自于 TPO 16 Planets in Our Solar System

　　Paragraph 4: Other dimensions along which the two groups differ markedly are density and composition. The densities of the terrestrial planets average about 5 times the density of water, whereas the Jovian planets have densities that average only 1.5 times the density of water. One of the outer planets, Saturn, has a density of only 0.7 that of water, which means that Saturn would float in water. Variations in the composition of the planets are largely responsible for the density differences. The substances that make up both group of planets are divided into three groups-gases, rocks, and ices-based on their melting points. The terrestrial planets are mostly rocks: dense rocky and metallic material, with minor amounts of gases. The Jovian planets, on the other hand, contain a large percentage of the gases hydrogen and helium, with varying amounts of ices: mostly water, ammonia, and methane ices.

　　Question: Paragraph 4 mentions which of the following as a reason why terrestrial planets are dense?

　　A. They are made up of three groups of substances.

　　B. They are composed mainly of rocky and metallic materials.

　　C. They contain more ice than Jovian planets.

　　D. They contain relatively small amounts of water.

　　解析：题干问的是类地行星密度较大的原因。那我们只需将做题重点锁定在原文描述“density”的信息上即可。原文中含有density的句子，第一句在说类地行星的密度和其他行星的密度比。第二句说的是土星密度。第三句说到行星结构的不同影响着密度的不同。后面进一步阐释组成行星的物质：气体，岩石以及冰。接着又提到类地行星主要由岩石组成。显然，这就是它密度大的原因。综合比较，应该选B。