今天我们学习托福阅读中另一种常见的段落逻辑框架-对比结构，对比结构的核心在于“比较”，即通过对比两个或多个事物、观点、现象等，来突出它们之间的相似点或差异点。因此在阅读时，同学们不仅要抓住对比对象是谁，还要搞清楚它们的差异点是什么，考点也会在此出现。
很多同学会把对比结构和转折结构混淆，记住下面这张表，秒辨两者！
真题实例区分：
👉对比结构：
"Medieval art focused on religious themes, whereas Renaissance art emphasized humanism."（两种艺术类型对比）
👉转折结构：
"Medieval art focused on religion; however, later artists began exploring secular topics."（同一艺术范畴的转变）
一、如何快速识别对比结构？
记住两个关键词：对象差异 + 信号词
1. 显性信号词，一眼锁定对比
这些线索词出现时请高亮标记：
差异强调词：Unlike, Whereas, In contrast, By comparison, Differ from
比较级/最高级：More...than..., Less...than..., Superior/Inferior to
分类提示词：Two different types/categories/approaches...（例："Scientists identified two distinct theories..."）
2. 内容特征：成对出现的“对立描述”
如果发现段落中频繁出现A和B的平行描述，且特征相反，大概率是对比结构：
结构对称：前半句讲A，后半句讲B（常用while连接）
（例："Carnivores rely on hunting, while herbivores depend on plants."）
重复对比维度：如“方法、特征、优缺点”等
（例：反复出现"method", "advantage", "strategy"等关键词）
二、小试牛刀
Compared with the East（此处指东罗马帝国）, however, the West faced a greater number of external threats along more permeable frontiers【首句总起对比】.1）Whereas the East could pursue war and diplomacy more effectively with their enemies on the long eastern frontier, the West was exposed to the more volatile tribal Germanic peoples on a frontier that stretched along the Rhine and Danube rivers for 1,000 miles. The East, however, only had to guard the last 500 miles of the Danube. //2）In addition, the East had many more human and material resources with which to pursue its military and diplomatic objectives. //3）The East also had a more deeply rooted unity in the Greek culture of the numerous Greek and Near Eastern cities that Rome had inherited from earlier Grecian empires. Latin culture had not achieved comparable penetration of the less urbanized West outside of Italy. The penetration of Germanic culture from the north had been so extensive along the permeable Rhine-Danube frontier that it was often difficult to distinguish between “barbarians” (speakers of German and other languages unrelated to Latin) and “Romans” in those regions by the fifth century anyway.
注释：拉丁文化Latin culture主要指古罗马文化Ancient Roman culture，它是希腊文化Greek culture的继承者和传播者，两者都是西方文明的重要支柱。
这是一篇典型的对比结构段落，从首句可以得出对比对象是东罗马帝国vs西罗马帝国，从however可以得出侧重点是西罗马帝国面临a greater number of external threats。拿下主旨句，这段的理解就完成了大半。本段难点在于，对比东、西罗马帝国时，一共比较了哪些方面？各自有什么特点？
接下来对比了两帝国在军事防御、资源方面和文化渗透的差异：
理解清楚东西罗马帝国各自对比特点之后，完成这道目的题就不在话下了。
In paragraph 3, why does the author discuss the Germanic culture?
A.To compare the less urbanized West outside of Italy to the more urbanized East
B.To explain why Roman military and political objectives necessarily changed in the fifth century
C.To emphasize that the Romans had more of a cultural disadvantage in the West than in the East
D.To explain why there were as many speakers of German as there were “Romans” on the western frontier
问题是“为何作者提问日耳曼文化”，根据分层可以定位至第三层文化层次的区别，东罗马帝国更具有希腊文化的统一性，而西罗马提过则受日耳曼文化渗透更多（即野蛮人），因此东罗马帝国更具文化优势，选择C选项。
A和B选项则是分别对应第一层、第二层内容，和文化层次无关。
D选项则是目的题中的易错特征“仅提到关键词，但和本段主旨无关”。
❗最后的小提醒：
对比结构的核心是求异，但偶尔会先描述相似再转折差异（如“Both A and B... However...”）。此时需警惕陷阱，重点看差异部分！
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