托福阅读修辞目的题是阅读考试中比较常见的一种题型，tpo则是托福阅读备考最权威的材料，所以托福小编综合二者，为大家集中整理了tpo阅读中考察的修辞目的题及其对应的解析，供大家参考使用。本文带来的是TPO20-3的修辞目的题，一起来看看吧。
TPO20-3 FOSSIL PRESERVATION
Paragraph 1
When one considers the many ways by which organisms are completely destroyed after death, it is remarkable that fossils are as common as they are. Attack by scavengers and bacteria, chemical decay, and destruction by erosion and other geologic agencies make the odds against preservation very high. However, the chances of escaping complete destruction are vastly improved if the organism happens to have a mineralized skeleton and dies in a place where it can be quickly buried by sediment. Both of these conditions are often found on the ocean floors, where shelled invertebrates (organisms without spines) flourish and are covered by the continuous rain of sedimentary particles. Although most fossils are found in marine sedimentary rocks, they also are found in terrestrial deposits left by streams and lakes. On occasion, animals and plants have been preserved after becoming immersed in tar or quicksand, trapped in ice or lave flows, or engulfed by rapid falls of volcanic ash.
2 In paragraph 1, what is the author’s purpose in providing examples of how organisms are destroyed?
○To emphasize how surprising it is that so many fossils exist
○To introduce a new geologic theory of fossil preservation
○To explain why the fossil record until now has remained incomplete
○To compare how fossils form on land and in water
解析：修辞目的题，修辞点所在句是一个例子，所以往前看，前一句说fossil遭破坏的方式和fossil一样多，后面就跟了很多破坏的方式，所以答案是A，阐释为什么如此多破坏之下还有这么多化石存在。往后看也可以，下一句说如果化石有骨架的话被保留的机会会大增，也就是一直都在说化石存留下来的机会，所以A是正确答案
[1] 如果想想生物在死之后被完全摧毁的种种方式，能够这样频繁出现化石是一件很令人惊讶的事。食腐动物和细菌的破坏、化学性腐烂、腐蚀以及其它地质因素都会非常不利于保存。不过，如果生物体碰巧具有矿化的骨骼并且死于可以迅速被沉积物掩埋的地方，摆脱被完全摧毁的几率便会大大增加。海底通常就具有上述的两方面条件，这里生活着很多带壳的无脊椎动物(没有脊椎的动物)，不断累积的似雨的沉积颗粒会把它们掩埋起来。虽然多数的化石是在海洋沉积岩中发现的，但是在溪流和湖泊留下的陆相沉积物中也发现过。有时，浸入焦油和流沙、陷入冰或熔岩流或被急速降落的火山灰吞噬的动植物得以保存下来。
Paragraph 2
The term “fossil” often implies petrifaction, literally a transformation into stone. After the death of an organism, the soft tissue is ordinarily consumed by scavengers and bacteria. They empty shell of a snail or clam may be left behind, and if it is sufficiently durable and resistant to dissolution, it may remain basically unchanged for a long period of time. Indeed, unaltered shells of marine invertebrates are known from deposits over 100 million years old. In many marine creatures, however, the skeleton is composed of mineral variety of calcium carbonate called aragonite. Although aragonite has the same composition as the more familiar mineral known as calcite, it has a different crystal form, is relatively unstable, and in time changes to the more stable calcite.
5 Why does the author mention “aragonite” in the passage?
○To emphasize that some fossils remain unaltered for millions of years.
○To contrast fossil formation in organisms with soft tissue and in organisms with hard shells
○To explain that some marine organisms must undergo chemical changes in order to fossilize
○To explain why fossil shells are more likely to survive than are fossil skeletons.
解析：修辞目的题，先看例子所在句子，说很多海洋生物的骨骼包含calcite，没有答案，往前看，前一句说一亿年前的沉积物中能发现骨骼不变的海生无脊椎动物，与A靠谱，但A本身不是一个观点，所以A不对;B和D完全没说，不对;强调的中心在例子所在句的下一句，说arogonite的晶体形状不同，相对不那么稳定，会变成更稳定的形式，所以答案是C，想稳定的话必须再变
[2] 术语“化石”常常意味着石化，字面意思就是变成了石头。生物体死后，软组织一般会被食腐动物和细菌吃掉。可能会留下蜗牛或蛤蜊空壳，如果空壳足够坚固并且能抵御分解，就有可能在很长一段时间内基本上保持原样。事实上，我们现在所知的在沉积物中发现的海洋无脊椎动物保存良好的壳已超过了1亿年之久。不过，很多海洋生物的骨骼是由称为霰石的各式碳酸钙矿物质组成的。虽然霰石与我们更为熟悉的矿物方解石具有同样的组成，但是它的晶型不同，相对不稳定，最终会变成更稳定的方解石。
以上就是托福阅读TPO20-3中的修辞目的题及其解析，大家可以在备考的时候参考复习，希望能够帮助大家的考前准备。最后前程百利祝大家都能取得理想的托福考试成绩。
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