作者目的题，也叫做修辞目的题，但其实在 TPO 中它的范围更广，除了举例说明概述题外，还有类似段落关系方面的题。既然是作者目的题，此题型首先考察的就是考生是否可以准确的进行换位思考，了解作者的意图。
我们将作者目的进行了归类，这就包括：提供信息（inform），定义（define），解释（explain），例证（illustrate），比较（compare），对比（contrast），批评 （criticize） 等。下文中我将对此题型的常见出题方法进行解析：
• Why does the author mention/include/use…？
• The author…in order to…
• The author uses the example to…？
The numbers of deer have fluctuated markedly since the entry of Europeans into Puget Sound country. The early explorers and settlers told of abundant deer in the early 1800s and yet almost in the same breath bemoaned the lack of this succulent game animal. Famous explorers of the North American frontier， Lewis and Clark arrived at the mouth of the Columbia River on November 14，1805， in nearly starved circumstances. They had experienced great difficulty finding game west of the Rockies and not until the second of December did they kill their first elk. To keep 40 people alive that winter， they consumed approximately 150 elk and 20deer.
The author tells the story of the explorers Lewis and Clark in paragraph 3 in order to illustrate which of the following points？
number of deer within the Puget Sound region has varied over time.
of the explorers who came to the Puget Sound area were primarily interested in hunting game.
e was more game for hunting in the East of the United States than in the West.
vidual explorers were not as successful at locating games as were the trading companies.
解析：根据较容易定位的人名到段落第三句“Famous explorers of the North American frontier， Lewis and Clark had experienced great difficulty finding game west of the Rockies and not until the second of December did they kill their first elk.”
意思是：北美边境有名的探险者，Lewis 和 Clark 在落基山西边很难找到捕猎动物并且直到十二月二号才捕到第一只鹿。
这是一个例子，所以我们就往前阅读看段落首句——段首句往往是段落中的重中之重。“The numbers of deer have fluctuated markedly since the entry of Europeans into Puget Sound country.”意思是：鹿的数量自从欧洲人进入 Puget Sound 地区后就发生了显著的波动。所以明显的这句话才是例子要支持的观点，显而易见我们可以得出选项 A 是正确答案。
Much of the world＇s great architecture has been constructed of stone because of its beauty， permanence， and availability. In the past， whole cities grew from the arduous task of cutting and piling stone upon. Some of the world＇s finest stone architecture can be seen in the ruins of the ancient Inca city of Machu Picchu high in the eastern Andes Mountains of Peru.
The doorways and windows are made possible by placing over the open spaces thick stone beams that support the weight from above. A structural invention had to be made before the physical limitations of stone could be overcome and new architectural forms could be created. That invention was the arch， a curved structure originally made of separate stone or brick segments. The arch was used by the early cultures of the Mediterranean area chiefly for underground drains， but it was the Romans who first developed and used the arch extensively in aboveground structures.
Roman builders perfected the semicircular arch made of separate blocks of stone. As a method of spanning space， the arch can support greater weight than a horizontal beam. It works in compression to divert the weight above it out to the sides， where the weight is borne by the vertical elements on either side of the arch. The arch is among the many important structural breakthroughs that have characterized architecture throughout the centuries.
Why does the author include a description of how the ＂doorways and windows＂ of Machu Picchu were constructed？
indicate that the combined skeletons and skins of the stone buildings of Machu Picchu were similar to igloos and adobe structures.
indicate the different kinds of stones that had to be cut to build Machu Picchu.
provide an illustration of the kind of construction that was required before arches were invented.
explain how ancient builders reduced the amount of time necessary to construct buildings from stone.
解析：我们可以利用题干中的“doorways and windows”of Machu Picchu 定位至段落第四行，按照之前的方法阅读会发现前文并不难理解，讲述了最早的建筑都是由石头构成还有石头盖房的好处，并且在秘鲁的安第斯山脉上有最好的石头建成建筑的遗迹。但是，悲伤的事发生了，在选项中并没有一个合适的。所以，在 ETS 出题的过程中有些作者目的题的答案是在例子的后面。于是就可以往后阅读，会发现文章中有这样的描写：
“A structural invention had to be made before the physical limitations of stone could be overcome and new architectural forms could be created. That invention was the arch，...” 也就是“（设计师们）必须在克服石头的物理限制以及新建筑形式发展之前发明出建筑结构，这就是拱形结构，……”那么，结合上下文之后作者为什么要提“马丘比丘的门和窗”呢？选择答案易如反掌是 C。
The astrolabe had long been the primary instrument for navigation， having been introduced in the eleventh century. It operated by measuring the height of the Sun and the fixed stars： by calculating the angles created by these points， it determined the degree of latitude at which one stood （The problem of determining longitude， though， was not solved until the eighteenth century.） By the early thirteenth century， Western Europeans had also developed and put into use the magnetic compass， which helped when clouds obliterated both the Sun and the stars. Also beginning in the thirteenth century， there were new maps refined by precise calculations and the reports of sailors that made it possible to trace one＇s path with reasonable accuracy.
Certain institutional and practical norms had become established as well. A maritime code known as the Consulate of the Sea， which originated in the western Mediterranean region in the fourteenth century， won acceptance by a majority of sea goers as the normative code for maritime conduct； it defined such matters as the authority of a ship＇s officers， protocols of command， pay structures， the rights of sailors， and the rules of engagement when ships met one another on the sea-lanes. Thus by about 1400， the key elements were in place to enable Europe to begin its seaward adventure.
Why does the author include the information that Western Europeans haddeveloped and put into use the magnetic compass？
provide an example of an instrument that was developed after caravels had begun traveling across oceans.
provide an example of an improvement that resulted directly from the invention of the astrolabe.
identify one of the technological advances that made sea trade with the East possible.
explain how the problem of determining longitude was solved.
解析：根据问题中的关键词 magnetic compass 可以定位到文章的第五行，但是由于句中的also，可知磁针罗盘和星盘是并列关系，即两者都是重要的航海定位工具，所以 C 选项是正确答案。此题即例子和观点合成一句话。