加拿大留學(xué)考試托福閱讀關(guān)于“不干凈”的段落

加拿大留學(xué)考試很多人對托福閱讀文章有一個根深蒂固的誤區(qū)，那就是每個段落有一個段落主旨，而這個段落主旨多數(shù)情況下是通過一個所謂的主旨句（topic sentence）來體現(xiàn)的。

為什么我們說這是一個誤區(qū)呢？我們來看一個典型的段落吧。

TPO 36-1 Soil Formation

Paragraph 1

Living organisms play an essential role in soil formation.The numerous plants and animals living in the soil release minerals from the parent material from which soil is formed,supply organic matter,aid in the translocation(movement)and aeration of the soil,and help protect the soil from erosion.The types of organisms growing or living in the soil greatly influence the soil’s physical and chemical characteristics.In fact,for mature soils in many parts of the world,the predominant type of natural vegetation is considered the most important direct influence on soil characteristics.For this reason,a soil scientist can tell a great deal about the attributes of the soil in any given area simply form knowing what kind of flora the soil supports.Thus prairies and tundra regions,which have characteristic vegetations,also have characteristic soils.加拿大托福

認(rèn)真讀一下這個段落，我們覺得大多數(shù)人都會認(rèn)為第一句話就是這段的主旨句，因為這個段落的內(nèi)容都是在圍繞著第一句話展開的，也就是典型的“總--分”結(jié)構(gòu)。如下：

TPO 36-1 Soil Formation

Paragraph 1

Living organisms play an essential role in soil formation.The numerous plants and animals living in the soil release minerals from the parent material from which soil is formed,supply organic matter,aid in the translocation(movement)and aeration of the soil,and help protect the soil from erosion.The types of organisms growing or living in the soil greatly influence the soil’s physical and chemical characteristics.In fact,for mature soils in many parts of the world,the predominant type of natural vegetation is considered the most important direct influence on soil characteristics.For this reason,a soil scientist can tell a great deal about the attributes of the soil in any given area simply form knowing what kind of flora the soil supports.Thus prairies and tundra regions,which have characteristic vegetations,also have characteristic soils.

不過，上面的這個想法是很危險的。你可以說這個段落是“總--分”結(jié)構(gòu)，第一句話是總，剩下的是分。但是你不太能說第一句話就是這段的主旨句。

為什么呢？我們來思考一下：

第一句的意思是“活的生物在土壤的形成中起到了重要的作用。”

如果第一句話是這段的主旨句的話，那就是說這個段落就是在說“活的生物在土壤形成中起到了重要的作用”。

可是，如果你去看這篇文章的后文（可以去TPO 36找到全文），你會發(fā)現(xiàn)，后面的段落分別還主要講了細(xì)菌，樹，動物等對土壤形成的影響。也就是說，這個第一句話實際上已經(jīng)囊括了后面的段落的核心意思。所以，與其說它是第一段的段落主旨，不如說它是全文的文章主旨。

加拿大留學(xué)考試托福閱讀關(guān)于“不干凈”的段落

可見，說這個第一句話是第一段的主旨句是偏頗的，是不利于抓住第一段真正的主旨的。實際上第一段真正的主旨應(yīng)該是原文中In fact那句話，即：

In fact,for mature soils in many parts of the world,the predominant type of natural vegetation is considered the most important direct influence on soil characteristics.

也就是說，第一段主要是聊植被對土壤形成起到了最關(guān)鍵的作用。然后第二段，第三段和第四段又主要分別展開細(xì)菌，樹，動物對土壤形成所起到的作用。這里作者暗含了它們都沒植被對土壤形成起到的作用大，植被是最大的影響因素。

按我們說的意思，這個段落的層次劃分如下：

TPO 36-1 Soil Formation

Paragraph 1

Living organisms play an essential role in soil formation.The numerous plants and animals living in the soil release minerals from the parent material from which soil is formed,supply organic matter,aid in the translocation(movement)and aeration of the soil,and help protect the soil from erosion.The types of organisms growing or living in the soil greatly influence the soil’s physical and chemical characteristics.In fact,for mature soils in many parts of the world,the predominant type of natural vegetation is considered the most important direct influence on soil characteristics.For this reason,a soil scientist can tell a great deal about the attributes of the soil in any given area simply form knowing what kind of flora the soil supports.Thus prairies and tundra regions,which have characteristic vegetations,also have characteristic soils.

這就是我們說的“不干凈”的段落了，你無論以哪句話為主旨句都沒法把段落“干凈”地單獨拎出來。如果你說第一句話是段落主旨，那這句話還包括了第二段，第三段和第四段。你沒法把第一段單獨地，“干凈地”拎出來。如果按我們說的In fact那句話是段落主旨，你又發(fā)現(xiàn)In fact之前的三句話不是只講植被，是一種總括。所以我們也沒法用In fact這句話就把第一段的所有內(nèi)容都“干干凈凈地”包括了。

這樣的段落在托福閱讀中比比皆是。你會發(fā)現(xiàn)，你好像幾乎永遠(yuǎn)都無法找到一個“干干凈凈“的段落。

再舉一個例子：

The Chaco Phenomenon

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For more than a century archaeologists have struggled to understand the circumstances surrounding the rise and collapse of Chacoan society—dubbed the Chaco Phenomenon.In particular,research has focused on determining why such an apparently inhospitable place as Chaco,which today is extremely arid and has very short growing seasons,should have favored the concentration of labor that must have been required for such massive construction projects over brief periods of time.Until the 1970s,it was widely assumed that Chaco had been a forested oasis that attracted farmers who initially flourished but eventually fell victim to their own success and exuberance,as they denuded the canyon of trees and vegetation to build large great houses.In the 1980s this reconstruction was largely dismissed in response to evidence that there had never been a forest in Chaco,and that canyon soils had poor agricultural potential.As scientific interpretations about Chaco changed,the focus of explanatory models changed from the attractiveness of the canyon for farmers to the position of the canyon within a regional network of dispersed agricultural communities.

分析一下這個段落，你很可能會覺得第一句話是總，后面是分。也就是如下分層：

The Chaco Phenomenon

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For more than a century archaeologists have struggled to understand the circumstances surrounding the rise and collapse of Chacoan society—dubbed the Chaco Phenomenon.In particular,research has focused on determining why such an apparently inhospitable place as Chaco,which today is extremely arid and has very short growing seasons,should have favored the concentration of labor that must have been required for such massive construction projects over brief periods of time.Until the 1970s,it was widely assumed that Chaco had been a forested oasis that attracted farmers who initially flourished but eventually fell victim to their own success and exuberance,as they denuded the canyon of trees and vegetation to build large great houses.In the 1980s this reconstruction was largely dismissed in response to evidence that there had never been a forest in Chaco,and that canyon soils had poor agricultural potential.As scientific interpretations about Chaco changed,the focus of explanatory models changed from the attractiveness of the canyon for farmers to the position of the canyon within a regional network of dispersed agricultural communities.

其實這么分層的話，就非常粗糙，根本抓不住這段真正的主旨。這個段落的第一句話實際上同樣也是囊括了后面的第3段，第4段和第5段，根本不能算是第2段的段落主旨。

認(rèn)真研究之后，細(xì)致的分層應(yīng)該如下：

The Chaco Phenomenon

Paragraph 2

For more than a century archaeologists have struggled to understand the circumstances surrounding the rise and collapse of Chacoan society—dubbed the Chaco Phenomenon.In particular,research has focused on determining why such an apparently inhospitable place as Chaco,which today is extremely arid and has very short growing seasons,should have favored the concentration of labor that must have been required for such massive construction projects over brief periods of time.Until the 1970s,it was widely assumed that Chaco had been a forested oasis that attracted farmers who initially flourished but eventually fell victim to their own success and exuberance,as they denuded the canyon of trees and vegetation to build large great houses.In the 1980s this reconstruction was largely dismissed in response to evidence that there had never been a forest in Chaco,and that canyon soils had poor agricultural potential.As scientific interpretations about Chaco changed,the focus of explanatory models changed from the attractiveness of the canyon for farmers to the position of the canyon within a regional network of dispersed agricultural communities.

第一層是一個大的總：科學(xué)家們關(guān)于圍繞著Chaco社會的興衰的來龍去脈不太能理解，尤其他們不太明白為什么Chaco這么一個鳥不拉屎的地方會聚集這么多人去建大房子。

第二層是對第一層的疑問的第一個假說：這個地方之所以聚集這么多人建大房子是因為這個地方曾經(jīng)是森林綠洲，后來森林被砍光建房子了，導(dǎo)致社會衰落。

第三層是對第一個假說的批判：80年代的證據(jù)表明了這個地方根本就沒有森林，所以科學(xué)家們開始從別的角度去尋找解釋，他們開始思考這個地方在整個區(qū)域交通網(wǎng)絡(luò)中的位置問題，這算是要引出第二個假說了。

而接下來的第3段就是緊接著聊第二個假說的，如下：

Paragraph 3

The adoption of a regional perspective in explaining the Chaco Phenomenon was based in part on the discovery of formal trails connecting many of the great houses in Chaco,as well as linking the canyon to smaller great houses located throughout the San Juan basin,the latter are referred to as Chaco“outliers.”These trails are densest around the concentration of great houses in the center,and the canyon itself is roughly at the center of the basin.Consequently,the canyon occupies the geographical and social center of the network formed by the connecting trails.The current consensus view is that religion provides the fundamental explanation for this centrifugal pattern.

所以，你發(fā)現(xiàn)沒，對于文章的第2段，你是無法用段落中的任何一句話去作為主旨句去概括整個段落的意思的。你能做的就只是把這個段落層次分出來，并理解層次和層次之間的關(guān)系，如下：

The Chaco Phenomenon

Paragraph 2

For more than a century archaeologists have struggled to understand the circumstances surrounding the rise and collapse of Chacoan society—dubbed the Chaco Phenomenon.In particular,research has focused on determining why such an apparently inhospitable place as Chaco,which today is extremely arid and has very short growing seasons,should have favored the concentration of labor that must have been required for such massive construction projects over brief periods of time.Until the 1970s,it was widely assumed that Chaco had been a forested oasis that attracted farmers who initially flourished but eventually fell victim to their own success and exuberance,as they denuded the canyon of trees and vegetation to build large great houses.In the 1980s this reconstruction was largely dismissed in response to evidence that there had never been a forest in Chaco,and that canyon soils had poor agricultural potential.As scientific interpretations about Chaco changed,the focus of explanatory models changed from the attractiveness of the canyon for farmers to the position of the canyon within a regional network of dispersed agricultural communities.

而為什么要把這三個層次放在這同一個段落中呢？這好像還真是隨機(jī)的，沒有一點道理。

我們完全可以把第一層單拎出來作為一個段落，也完全可以把第三層拎出來跟后面第3段的內(nèi)容放在一起作為一個段落。

所以，你如果還是天真地去托福閱讀的段落中去找所謂的“主旨句（Topic sentence）”，那你真的是要掉大坑了！你要么找不到所謂主旨句，要么就算找到了，它也無法提供給你關(guān)于段落主旨的有效信息。