获取方案

在GMAT的考试过程中，并不是所有同学的英文基础都足以完全看懂每一道题；事实上，有一些涉及到专业背景知识的题目（医学类、考古类、生物类等等）会包含大量的陌生的专有名次，很多时候大部分人都是看不太懂的。但是由于逻辑的部分只考察逻辑而非词汇或专业知识，在一些特殊的模型下，我们可以做到看不懂题目依然能选到正确的答案。今天我们就来看一种经常出现于增强、假设及结论题里面的特殊模型——AB-AC模型。

一、AB-AC模型特点及场景

特点：因为A和B有关系，A又和C有关系，那么通过A的中介，B和C应该有关系。

场景：经常用于一些对专业知识要求非常高但不同对象之间的逻辑关系相对简单的情况。

二、例题

Yeasts capable of leavening bread are widespread, and in the many centuries during which the ancient Egyptians made only unleavened bread, such yeasts must frequently have been mixed into bread doughs accidentally. The Egyptians, however, did not discover leavened bread until about 3000 B.C. That discovery roughly coincided with the introduction of a wheat variety that was preferable to previous varieties because its edible kernel could be removed from the husk without first toasting the grain.

Which of the following, if true, provides the strongest evidence that the two developments were causally related?

(A)Even after the ancient Egyptians discovered leavened bread and the techniques for reliably producing it were well known, unleavened bread continued to be widely consumed.

(B)Only when the Egyptians stopped the practice of toasting grain were their stone-lined grain-toasting pits available for baking bread.

(C)Heating a wheat kernel destroys its gluten, a protein that must be present in order for yeast to leaven bread dough.

(D)The new variety of wheat, which had a more delicate flavor because it was not toasted, was reserved for the consumption of high officials when it first began to be grown.

(E)Because the husk of the new variety of wheat was more easily removed, flour made from it required less effort to produce.

在这道题里就涉及到了发酵面包的知识。原文部分语义如下：

发酵面包的酵母应用的很广泛，在古埃及人只会做非发酵面包的几个世纪中，这些酵母一定时常被偶然混合进面团里。然而，古埃及人直到公元前3000年才发明发酵的面包。这个发明大概和一种比之前更好的新小麦的引入同时发生，这种新的小麦的麦粒不用烘烤就可以剥离出来。

这个题目涉及到了yeast、leaven\kernel等词汇可能一些同学不太熟悉，但这个题里面的几个对象之间的逻辑关系非常简单：

首先题目问的是增强two developments(leavened bread & introduce new wheat）之间有关，所以首先作为结论，leavened bread ---introduce new wheat相关。那么到原文里面寻找为什么相关，不难找到最后一句话说coincide的原因是introduction of a wheat后面wheat的特点：edible kernel remove without toasting，所以new wheat和remove without toasting相关。得到逻辑链如下：

introduce new wheat---leavened bread

|

remove without toasting

即AB-AC模式。正确选项最常见的就是BC搭桥，即C：heating=toasting，C在讲toasting和leaven之间的关系，搭桥增强。

以上就是关于AB-AC模型的应用。