一般而言说明文会说明某个现象，文章的第一段是：介绍背景及引出下文;之后的主体段，结构也很清晰,下面小编就和大家分享托福阅读说明文体裁解析，希望能够帮助到你们，快来一起学习吧。
托福阅读说明文体裁解析
阅读：官方真题Official-19 The Roman Army's Impact on Britain
In the wake of the Roman Empire's conquest of Britain in the first century A.D., a large number of troops stayed in the new province, and these troops had a considerable impact on Britain with their camps, fortifications, and participation in the local economy. Assessing the impact of the army on the civilian population starts from the realization that the soldiers were always unevenly distributed across the country. Areas rapidly incorporated into the empire were not long affected by the military. Where the army remained stationed, its presence was much more influential. The imposition of a military base involved the requisition of native lands for both the fort and the territory needed to feed and exercise the soldiers' animals. The imposition of military rule also robbed local leaders of opportunities to participate in local government, so social development was stunted and the seeds of disaffection sown. This then meant that the military had to remain to suppress rebellion and organize government.
留下 these troops had a considerable impact on Britain;也就是第一句说的是罗马军队对英国有影响。这句话相当于对题目的阐述，交代了文章的整个大背景。 之后2～4句其实交代前提，开始具体的说开，要估算军队对平民的影响首先要了解一个事实：士兵不是平均分布的。那既然不是平均分布，肯定是有多有少的。所以，第三句接着说了有些地方士兵少：很快融入帝国的区域;第四句说有些地方士兵多影响大：军队驻扎的地方。第5～7句说回重点，也就是what，到底有哪些影响：军营先要征地;然后会抢走当地领导参与政府的机会;之后社会发展受阻，人民不满而反抗，最后军事镇压。
首段的第一句话，虽然句子很长，但其实只需要
所以总共7句话的段落，分层三个层次，主旨句+前提说明+重点阐述。事实上，段落第一句就完成了background+introduction双重目的：英国被罗马帝国征服+ 士兵的营地/防御工事以及参与当地经济所造成的影响。
Economic exchange was clearly very important as the Roman army brought with it very substantial spending power. …… Such activities had a major effect on the local area, in particular with the construction of infrastructure such as roads, which improved access to remote areas.
第二段一开始就交代了经济交换的影响：强大的购买力，以及帮助修建基础设施。(要想富，先修路)
Each soldier received his pay, but in regions without a developed economy there was initially little on which it could be spent. …… These settlements acted like small towns, becoming centers for the artisan and trading populations.
第三段还是在讲经济：刚来的时候士兵有钱没地方花;最后军队驻扎地变成了小镇。
The army also provided a mean of personal advancement for auxiliary soldiers recruited from the native peoples, as a man obtained hereditary Roman citizenship on retirement after service in an auxiliary regiment. …… By the later Roman period, frontier garrisons (groups of soldiers) were only rarely transferred, service in units became effectively hereditary, and forts were no longer populated or maintained at full strength.
第四段开始讲另一个重大影响：当地人通过当兵获得可继承的罗马公民地位。
This process of settling in as a community over several generations, combined with local recruitment, presumably accounts for the apparent stability of the British northern frontier in the later Roman period. It also explains why some of the forts continued in occupation long after Rome ceased to have any formal authority in Britain, at the beginning of the fifth century A.D. The circumstances that had allowed natives to become Romanized also led the self-sustaining military community of the frontier area to become effectively British.
第五段，做了个小总结，讲这种融合过程及当地招募促进了北部边境的稳定。
托福阅读：5种题型的技巧
(1)主旨题。主旨题有三种：A、作者的意图;B、文章标题;C、文章的中心思想。这种题一般为第一道题，建议考生把这道题放在最后做，因为做其他题时，考生会逐步了解文章的各个细节，在做题的过程中就会对文章个总的理解，最后处理主旨题可谓水到渠成、万无一失。
(2)列举题。列举题有两种：A、一正三误;B、三正误。也可分为四类。第一类：一句话列举。根据某个选项的语言提示，回归文章找到一句话，这句话包含三个选项的内容;第二类：局部列举。根据题意，回归文章发现连续两三句话涉及三个选项的内容;第三类：段落列举。题干语言在某自然段首句重现。这个句子为段落主题句，即三个选项的内容在这段出现，不涉及到其他段落;第四类：文章列举。选项内容涉及整个文章。一句话列举题和段落列举题有明显的信号词帮助答题，根据题序做题，不必区别对待。文章列举题和局部列举题则应放其他题做完之后再处理。
(3)文章结论题。文章结论题即根据文章可以推断出下面哪个选项结论是正确的，题干没有任何语言信号词。这种题有以下几种布局：为文章第一道题时，相当于文章主旨题，应放在最后一道题时，有可能针对文章最后部分，也有可能针对整篇文章，但不大可能涉及文章其他部分的细节。所以文章结论题应该具体情况具体分析，并不一定是面对整个文章。
(4)作者态度题。作者态度题分为两种：A、局部作者态度题;B、整体作者态度题。文章最后一道题问及作者态度时为整体作者态度题，它涉及通篇文章，要根据整个文章数个语言点串起来的一根主线答题，也就是作者行文的口气。考生千万不可以根据某一个语言点答题，因为整体作者态度题不是考核某一个点，而是考整体感觉。局部作者态度题位置比较灵活，往往问及作者对文章中某一个具体内容的看法，题干通常信号请将考生带回文章某一区域，考查考生对某个语言点的理解。有时候，某个选项从作者的表达相悖，因此，做作者态度题时，考生一定注意不要把自己作为读者的分析、观点强加于作者。
(5)文章想方设法题。文章结构题三种：A、文章前面的段落内容是什么?B、文章下面接着将要讲什么?C、文章组织结构是什么?推断文章前面的内容立足于文章首句，因为文章首句承上启下，尤其注意首句中诸如this、so、other than之类的结构词。预测下文的内容则分两步走：第一、读文章每段首句，文章每段首句表示文章内容的逻辑走向。如果文章讲述某一事物的两个阶段或方面，下文将介绍这一事物的第三个阶段或方面。我们把预测下文内容的题称之为坐标题，即竖看文章每段首句，横看文章最后一句，其他句子是文章所讲内容，而不是下面将要讲的内容，往往选项干扰来自文章所讲内容。至于文章的组织结构题，只需要读文章每段首句即可，因为这些句子是文章框架。
托福阅读：句意解释题技巧
这类型题目的题干表达为：Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
解决这类题目的三种方法：
第一种：在保持原句序基本不变的前提下进行重点词汇或者词组的同义替换;
第二种：在句序不变的前提下再进行重点词汇或者词组的同义替换;
第三种：对原句进行总结性重复。
下面我们通过一个例子来看这些方法的具体应用：
Small marketers should be less concerned with whether U.S. and European consumers are alike and more concerned with monitoring the variety of factors that account for potential similarities and differences. Attention to the dynamic nature of those factors will produce opportunities for the alert marketer.
Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
1. A marketer who is not so smart should be more concerned with the difference of eating habits between U.S. and European consumers and less concerned with monitoring the variety of factors that account for potential similarities and differences.
2. It is not important whether U.S. and European consumers have a similar eating habit. I t is the potential similarities and differences that people should be more concerned with.
3. Marketers should focus on the factors that account for difference rather than the difference themselves.
4. Monitoring the variety of foods could explain the potential similarities and differences.
解题：
首先，我们来分析这个句子，整个主句的主语为Small marketers，谓语为be concerned with，宾语为factors，这个分析完成之后，我们采用同意替换的方法，替换其中的重点词组-谓语be concerned with，其同义词为focus on。这样替换完之后把两个句子的意思进行比较，得出正确答案C。这道题目采用了第一种方法。
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