舉例說明概述題，也叫例證題，被ETS稱為“修辭目的題”(rhetorical purpose question)，基本形式如下：
The author uses X as an example of…
Why does the author mention X？
The author discusses X in paragraph 2 in order to…
…sensitivity to physical laws is thus an important consideration for the maker of applied-art objects. It is often taken for granted that this is also true for the maker of fine-art objects. This assumption misses a significant difference between the two disciplines. Fine-art objects are not constrained by the laws of physics in the same way that applied-art objects are. Because their primary purpose is not functional， they are only limited in terms of the materials used to make them. Sculptures must， for example， be stable， which requires an understanding of the properties of mass， weight distribution， and stress. Paintings must have rigid stretchers so that the canvas will be taut， and the paint must not deteriorate， crack， or discolor. These are problems that must be overcome by the artist because they tend to intrude upon his or her conception of the work. For example， in the early Italian Renaissance， bronze statues of horses with a raised foreleg usually had a cannonball under that hoof. This was done because the cannonball was needed to support the weight of the leg…”
Why does the author discuss the bronze statues of horses created by artists in the early Italian Renaissance ？
To provide an example of a problem related to the laws of physics that a fine artist must overcome
To argue that fine artists are unconcerned with the laws of physics
To contrast the relative sophistication of modern artists in solving problems related to the laws of physics
To note an exceptional piece of art constructed without the aid of technology
根據問題中的關鍵字bronze statues of horses定位段末，這裡有標誌詞for example，說明它是對前面所說的內容進行例證。前一句These are problems that must be overcome by the artist…就是概述：藝術家必須克服這些問題，因為這些問題破壞他們對藝術作品的構思。這裡所說的問題就是上文談論的物理規律對美術的限制，如必須考慮製作材料的物理特性。而本題對應的原文以例子說明這一點：由於銅的特性，馬抬起的前腿下必須有支撐物。綜上所述，例子說明它前面的概述，第一個選項符合此意，為正確答案。
One of the most puzzling aspects of the paintings is their location. Other rock paintings—for example， those of Bushmen in South Africa—are either located near cave entrances or completely in the open. Cave paintings in France and Spain， however， are in recesses and caverns far removed from original cave entrances.
Why does the author mention Bushmen in South Africa in paragraph 2？
To suggest that ancient artists from all over the world painted animals on rocks
To contrast the location of their rock paintings to those found at Lascaux
To support the claim that early artists worked in cramped spaces
To give an example of other artists who painted in hidden locations
與上一題類似，本題的例子Bushmen in South Africa在原文也有標誌詞for example，因此這一例子的目的是為了說明它前面的那句話，即這些繪畫的位置令人費解。作者以對比的手法來說明這一點：Bushmen in South Africa的繪畫常位於洞口或洞外，而法國和西班牙的洞穴繪畫(本文所說的繪畫)卻位於遠離最初洞口的深處。由此可見，Bushmen in South Africa的例子是為了說明Lascaux繪畫位置的怪異。第二個選項符合此意，為正確答案。
Scholars offer three related but different opinions about the mysterious origin and significance of these paintings. One opinion is that the paintings were a record of seasonal migrations made by herds. Because some paintings were made directly over others， obliterating them， it is probable that a painting’s value ended with the migration it pictured. Unfortunately， this explanation fails to explain the hidden locations， unless the migrations were celebrated with secret ceremonies.
Why does the author mention secret ceremonies？
To present a common opinion held by many scholars
To suggest a similarity between two opinions held by scholars
To suggest a possible explanation for a weakness in an opinion expressed in the passage
To give evidence that contradicts a major opinion expressed in the passage
問題中的關鍵字secret ceremonies出現於段落末句的從句中：unless the migrations were celebrated with secret ceremonies。在同一句子的主句部分，作者指出：不幸的是，這一解釋未能說明為何繪畫的位置要隱蔽…，這等於說這一解釋不能成立；接著在問題所對應的從句中補充說明上述解釋成立所必須滿足的條件：除非遷徙的慶祝是秘密進行的。這等於說這一解釋缺乏這一條件。第三個選項符合此意，為正確答案。
Mass transportation revised the social and economic fabric of the American city in three fundamental ways. It catalyzed physical expansion， it sorted out people and land uses， and it accelerated the inherent instability of urban life. By opening vast areas of unoccupied land for residential expansion， the omnibuses， horse railways， commuter trains， and electric trolleys pulled settled regions outward two to four times more distant from city centers than they were in the pre-modern era. In 1850， for example， the borders of Boston lay scarcely two miles from the old business district； by the turn of the century the radius extended ten miles. Now those who could afford it could live far removed from the old city center and still commute there for work， shopping， and entertainment. The new accessibility of land around the periphery of almost every major city sparked an explosion of real estate development and fueled what we now know as urban sprawl. Between 1890 and 1920， for example， some 250，000 new residential lots were recorded within the borders of Chicago， most of them located in outlying areas. Over the same period， another 550，000 were plotted outside the city limits but within the metropolitan area. Anxious to take advantage of the possibilities of commuting， real estate developers added 800，000 potential building sites to the Chicago region in just thirty years – lots that could have housed five to six million people.
18. Why does the author mention both Boston and Chicago？
(A) To demonstrate positive and negative effects of growth.
(B) To show that mass transit changed many cities.
(C) To exemplify cities with and without mass transportation.
(D) To contrast their rates of growth
問題中的關鍵字Boston與Chicago是兩個例子，它們前面分別有提示詞for example。由於兩個例子位於同一段，而且不在一處，因此只能說明本段主題，也就是首句：Mass transportation revised the social and economic fabric of the American city in three fundamental ways。選項(B)符合此意，為正確答案。