如何通过段落快速把握托福阅读文章主旨

　　例一(总-分结构)

　　Paragraph 7: About 90 percent of modern humans are right-handed: we are the only mammal with a preferential use of one hand. The part of the brain responsible for fine control and movement is located in the left cerebral hemisphere, and the findings above suggest that the human brain was already asymmetrical in its structure and function not long after 2 million years ago. Among Neanderthalers of 70,000–35,000 years ago, Marcellin Boule noted that the La Chapelle-aux-Saints individual had a left hemisphere slightly bigger than the right, and the same was found for brains of specimens from Neanderthal, Gibraltar, and La Quina.

　　What is the author's primary purpose in paragraph 7?

　　(A) To illustrate the importance of studying the brain

　　(B) To demonstrate that human beings are the only mammal to desire fine control of movement

　　(C) To contrast the functions of the two hemispheres of the brain

　　(D) To demonstrate that right-hand preference has existed for a long time

　　根据一般段落的总-分结构，可以判断首句为主题句，所以第四个选项为正确答案。文中主要描述大脑左半球的功能，未与大脑右半球的功能进行比较，所以第三个选项为干扰选项。

　　例二(总-分结构)

　　Paragraph 6: Moreover, getting petroleum out of the ground and from under the sea and to the consumer can create environmental problems anywhere along the line. Pipelines carrying oil can be broken by faults or landslides, causing serious oil spills. Spillage from huge oil-carrying cargo ships, called tankers, involved in collisions or accidental groundings (such as the one off Alaska in 1989) can create oil slicks at sea. Offshore platforms may also lose oil, creating oil slicks that drift ashore and foul the beaches, harming the environment. Sometimes, the ground at an oil field may subside as oil is removed. The Wilmington field near Long Beach, California, has subsided nine meters in 50 years; protective barriers have had to be built to prevent seawater from flooding the area. Finally, the refining and burning of petroleum and its products can cause air pollution. Advancing technology and strict laws, however, are helping control some of these adverse environmental

　　In paragraph 6, the author’s primary purpose is to

　　(A)provide examples of how oil exploration can endanger the environment

　　(B)describe accidents that have occurred when oil activities were in progress

　　(C)give an analysis of the effects of oil spills on the environment

　　(D)explain how technology and legislation help reduce oil spills

　　根据段落的总-分结构(段落首句中的复数名词problems说明本段落的结构是总-分结构——首句总论，其他句子分述几个problems)，可以确定首句为段落主题句，即本段的写作目的，第一个选项符合此意，为正确答案。第二个选项只是论证本身的内容，不是段落首句所说的写作目的。第三个选项与第四个选项都只是段落论述中的细节。

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