托福阅读功能作用题技巧

　　托福阅读功能作用题技巧，我们来康康一道人见人怕的功能作用题～

　　Why does the author mention "aragonite" in the passage?

　　首先，以题干中的“aragonite”，寻找所在意群的观点句。

　　Fossil Preservation　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. The 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 a 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.

　　原文中直接标注“aragonite ”位置，该句中以“however”插入形式引出「句间转折」。「句间转折」和「句内转折」理解的重点都是找反义词组，只不过「句内转折」反义词组在一句话内成对出现，而「句间转折」是在前后两个意群中分别出现。

　　在这段话中，我把however前称为「转折前意群」，however后称为「转折后意群」。再次套用转折逻辑的套路，要想做对题一定要理解转折中的反义词组。在转折前后意群查找中，可以识别出unchanged=unaltered  VS  unstable=change。而“aragonite”出现在转折后意群，则其作为栗子强调”unstable/change“这一关键。

　　A To emphasize that some fossils remain unaltered for millions of years

　　B To contrast fossil formation in organisms with soft tissue and in organisms with hard shells

　　C To explain that some marine organisms must undergo chemical changes in order to fossilize

　　D To explain why fossil shells are more likely to survive than are fossil skeletons

　　秒杀时刻到了！！！四个选项无需精读，重点看有没有出现关键词“unstable/ change“即可，所以马溜溜确定C选项，必须做对！！！