上一讲大家讲到可以借助句子在段落中的地方来判断段落的主题句。其实此外，段落中的关键字也是确定主题句的要紧线索。这一讲中，大家会重点剖析这个问题，期望同学们将来可以培养起对这类词语的敏锐的感觉，掌握有效率地阅读。
标志词：文章中有的词语对于大家正确判断一段话的主题是至关要紧的。在雅考虑试的文章中，主要有三类：强转折性的词、表示重要程度结构的词和表示人物看法结论性的词。
A. 强转折性的词
强转折的词主要包含but, however, yet, in fact等。这种词一方面表示其前后连接的内容是相反的关系。其次，强转折的词强调的是后面的内容，所以but之类的词后面的内容应该是大家阅读的重点。尤其是假如这种词出目前一段话的中前部，那样此句多半是整段话的论点，也就是整段的主题句。
应该注意的是，像although, though, despite, in spite of, albeit1, while这种词不同于强转折的词，
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Congress can pass laws, regulators can beef up enforcement, and shareholders2 can demand more accountability. But when it comes right down to it, making sure a company is operating well is really an inside job. Thats where internal auditing3 comes in. It doesnt sound glamorous4, but its an expanding field beckoning5 to people with a lot of pent up we-can-do-better energy. Internal auditors6 keep an eye on a companys controls-not just financial systems, but all sorts of functions designed to make the business run smoothly7 and protect the interests of shareholders.
...
All good fun. But in the aftermath of the Columbia disaster, the value of commercial research on missions has come into question. STS-107-the final flight of the Columbia-had 80 experiments on board, including five that were conducted by the astronauts for private companies, funded almost entirely8 by NASA. One was for International Flavors Fragrances9 , which extracted the smell of a rose in space and was back seeking new scents10. The other commercial experiments involved studies of ways to fight fire using fine Water mist, grow proteins with greater resilience to disease, manufacture crystals for such uses as hydrogen fuel storage and advance cancer-cell research. Is all this worth pursuing in space?
B. 表重要程度的结构
Are Americans a nation of frivolous11 porcers who selfishly pursue the bluebird of happiness, oblivious12 to their childrens needs? Divorce opponents like Judith Wallerstein seem to think most parents see porce as a marvelous opportunity for the whole family. How immature13 do they think people are ?All over America, unhappy spouses14 lie awake at night wondering if they and their kids can afford porce financially, socially, emotionally. Where will they live, how will they pay the bills, will the kids fall apart, will there be a custody15 battle, what will their families say? The very fact that so many people leave their marriage for a future with so many pitfalls16 proves that porce is anything but a whim17. Most people I know who split up spent years working up to it.
The truth is that the economic boost from spinoffs, is untraceable. The Berlei bra, for instance, uses a Dupont material called CoolMax, which was derived18 from a fabric19 developed to improve thermal20 clothing by Outlast21 Technologies in collaboration22 with NASAs Johnson Space Center. The proportion of Berlei bra sales accurately23 described as a NASA spinoff is anyones guess, but critics say returns cant even come close to covering the cosplayt of a shuttle flight.
The very fact that如此的结构一般用来提示要紧内容的出现。所以当类似的结构出目前段落首末地方的时候，该句极大概是全段的主题句，也就是主题句。类似的结构还有The point/problem/concern/idea/key factor is that, what matters/accounts is, what is extraordinary is等等。
C. 表示人物看法结论性的词:
The Welsh forces in Dyfed-Powys and Gwent both had impressively shape spidergrams thanks to comparatively good records on reducing and investigating crime. The force with the most dimming graph was Avon and Somerset, which was once regarded as a metropolitan24 force but had been grouped under the new scheme with areas including Norhampton shire and West Mercia which have much lower crime levels. Avon and Somerset, which includes Bristol,
pointed25 out that graph reflected the fact that the force and suffered form a wave of street crime that had subsequently been greatly reduced.
类似的结构还有believe, suggest, conclude, hold, show, reveal, find, find out, discover等。
