help！！！TPO20 fossil preservation 第二题第五题求教！

素黑久UID：3389790

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.



[url=]Q2 In paragraph 1, what is the author’s purpose in providing examples of how organisms are destroyed?[/url]

○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


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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





这是看到的网上的解释 但是还是觉得为什么B不行呢 这句话后面不就是要开始说新的保护方法了吗？求教！


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.

[url=]Q5 Why does the author mention “aragonite” in the passage?[/url][U1]

○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.


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[U1]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





同样在网上看到的解释，但是还是不理解为什么A就不对。什么叫“A本身不是一个观点 所以不对”？谢谢各位同学！！

素黑久UID：3389790

自己来顶一下

treemantanUID：2770681

个人感觉啊。。

看了下这一段，这一段就是围绕第一句写的，所以不管什么都是为了explain这个的（当然包括例子，中间的那么多however都是例子之间的差别的对比，并为引入新观点），而答案肯定是这一句的同义改写，第一句的主干it is remarkable that  fossils are as common as they are ，而只有答案A是同义改写吧。B的原因是这个introduce new，我并未看出有引入介绍这个trend，归根到底都是在第一句的大环境下写的，所以B弃之吧。

第二题的关键主要是however，however表示这个例子是为了强调后面的部分，所以不可能是强调这句前面的那个观点

素黑久UID：3389790

treemantan 发表于 2013-1-18 08:42
个人感觉啊。。

看了下这一段，这一段就是围绕第一句写的，所以不管什么都是为了explain这个的（当然包括 ...

第一个懂一点了 第二个还是不太懂。。我再好好想想！谢谢！！

素黑久UID：3389790

继续自己顶。。

hycqyUID：2819662

素黑久 发表于 2013-1-18 18:21
继续自己顶。。

第一题 我觉得那个解释和你都没有理解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. 的意思  这句话说的根本就不是什么“fossil遭破坏的方式和fossil一样多”  说的是如果我们考虑生物死后存在的方式 会发现其实形成化石的不比分解的少
注意destroyed after death和变成化石是并列的两种方式  换句话说 变成化石就是escaping complete destruction 而destroyed after death就是不形成化石 而不是说已经成化石的东西遭破坏还是被保留
整段根本没有说fossil preservation的事情 B里面的fossil preservation意思是对已经形成化石的东西的保留

hycqyUID：2819662

素黑久 发表于 2013-1-18 18:21
继续自己顶。。

第二题 some fossils remain unaltered for millions of years这个叙述本身是对的 但是作者提这个aragonite并不是为了强调这个叙述啊
注意这段话、的结构 先解释一下石化的含义 然后说石化之后可以保存很长时间 于是给一个例子就是 some fossils remain unaltered for millions of years  至此A选项的内容已经出现了 但是作者还没有提到aragonite
接下来作者说了一下有些化石是怎么变硬的 这时候才提到了aragonite这种物质  说到了aragonite由于晶体结构和calcite不同 不如calcite稳定 要长时间后变成calcite才稳定 这正是C的内容

素黑久UID：3389790

hycqy 发表于 2013-1-19 02:31
第一题 我觉得那个解释和你都没有理解When one considers the many ways by which organisms are complet ...

我懂了！！谢谢版主！！看来我还是练习的太少了。。