之前讲过很多细节题的错题，今天老师带大家一起学习一下如何应对【目的题】。

　　目的题是一种托福阅读中每一次考试一定会考到的题目，这个题目考察学生能否综合考虑上下文的整体意思，理解信息之间的逻辑关系，而不仅仅是孤立地看待某个词或句子。

　　在讲解目的题中，我们比较熟悉的是对举例进行提问，问例子的作用，然而，有的时候也会考到其他的逻辑，比如转折，因果。

　　接着我们来看一个例题，这道题是对转折后进行提问，作者为了强调转折后的内容。

　　易错题解析来啦

　　Question

　　TPO31 Savanna Formation T2

　　Savannas typically experience a rather prolonged dry season. One theory behind savanna formation is that wet forest species are unable to withstand the dry season, and thus savanna, rather than rain forest, is favored on the site. Savannas experience an annual rainfall of between 1,000 and 2,000 millimeters, most of it falling in a five- to eight-month wet season. Though plenty of rain may fall on a savanna during the year, for at least part of the year little does, creating the drought stress ultimately favoring grasses. Such conditions prevail throughout much of northern South America and Cuba, but many Central American savannas as well as coastal areas of Brazil and the island of Trinidad do not fit this pattern. In these areas, rainfall per month exceeds that in the above definition, so other factors must contribute to savanna formation.

　　3. In paragraph 2, the author mentions savannas in Central America, Brazil, and the island of Trinidad in order to:

　　A. argue that these savannas are similar to those in South America and Cuba

　　B. point out exceptions to the pattern of savanna formation in areas with drought stress

　　C. provide additional examples of savannas in areas with five-to-eight-month wet seasons

　　D. indicate areas where savannas are being gradually replaced by rain forests

　　思路解析

　　题目类型：目的题

　　干扰选项：A或者C

　　干扰类型:误以为被问到的句子是举例逻辑

　　解这道题时，我们采取定位-理清句间逻辑(找逻辑词)-核对选项的解题步骤来做题。

　　先用 savannas in Central America, Brazil, and the island of Trinidad 作为关键词定位到倒数第二句，也就是我们划了横线的这句话：but many Central American savannas as well as coastal areas of Brazil and the island of Trinidad do not fit this pattern.看到这半句话和前半句话中间有 but 的转折逻辑，转折句直接说明 Central America，Brazil 的沿海地区的草原和前面介绍的模式是不一样的。我们再往后面看一下，后文对提到的美州中部和巴西的沿海地区草原的不一样又做了进一步的说明，In these areas, rainfall per month exceeds that in the above definition, so other factors must contribute to savanna formation翻译过来就是：这些地方的草原每个月的降雨超过了前面的定义(干旱)。对应 B 选项(指出在有干旱压力的地区草原形成模式的例外情况)。

　　很多同学在做目的题时在技巧的运用中不够灵活，一般都是直接往前一句话找，就选择了A选项，还有学生则是再往前看了一句，选择了C选项，这种不管句子之间的逻辑关系，直接往前看几句，还是很容易错题的。如果题干中被问到的内容与上下文存在转折逻辑，作者是为了强调反驳前者，引起转折后的信息。

　　那我们用相同的方法再来解答后面的一道题目。

　　真题演练

　　TPO 35 Seasonal Succession in Phytoplankon-4

　　【Paragraph 3】Another suggested reason is the change in nutrient level over the year, with differing concentrations favoring different phytoplankton species. While this factor may also contribute, observations suggest that phytoplankton populations rise and fall much more quickly than nutrient concentrations change.

　　4. Why does the author provide the information that “phytoplankton populations rise and fall much more quickly than nutrient concentrations change”?

　　A. To argue that the nutrient level not determine phytoplankton succession.

　　B. To argue that the succession of phytoplankton is actually the cause of changes in the nutrient level.

　　C. To indicate that phytoplankton populations are very sensitive to changes in the nutrient level.

　　D. To imply that changes in the nutrient level explain the succession of phytoplankton.

　　题目类型：目的题

　　干扰选项：D

　　干扰类型：逻辑理解有误

　　选 D 的人可能认为作者提到“浮游植物种群的上升和下降速度比营养水平的变化快得多”是在暗示营养水平的变化可以解释浮游植物的演替。他们误以为这种联系是因果关系，即认为营养水平的变化导致了浮游植物种群的变化，因此解释了浮游植物的演替。但是是因果关系的话，原因和结果之间的方向应该是一致的。比如说因为天气不好，我就不出去。而这个句子中则是出现了不一致，说到的是浮游植物群上升下降速度比营养水平变化要快很多。所以因果关系是不成立的。

　　那我们仍然按照定位-找逻辑词-核对选项的步骤进行解题，

　　定位句为划线句，该内容的前半句有个while this factor may also contribute, 是个让步句，后半句是个转折，和前面的内容构成相反。也就是说被问到的内容是反对前一句话的观点：Another suggested reason is the change in nutrient level over the year, with differing concentrations favoring different phytoplankton species. 这句话的意思是说一年中营养物质的变化，导致了浮游生物的演替现象。定位句是反对这个观点，那就是不认为是营养物质改变而导致的，由此就可以判断答案为A选项。

　　通过这两个题，可以强化学生对于转折关系的把控，提醒我们做目的题这种考察段落结构和逻辑的题型的时候，多学会用逻辑关系去解决目的题。而不只是刻板使用例子证明观点这一种常见的逻辑。这也意味着，咱们需要提高句子理解能力和快速阅读能力。

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