上一讲我们讲到可以利用句子在段落中的位置来判断段落的主题句。其实除此之外，段落中的关键词也是确定主题句的重要线索。这一讲中，我们会重点分析这个问题，希望同学们以后能够培养起对这些词汇的“敏感的感觉”，学会有效率地阅读。
² 标志词：文章中有些词汇对于我们正确判断一段话的主题是至关重要的。在雅思考试的文章中，主要有三类：强转折性的词、表示重要性结构的词和表示人物观点结论性的词。
A. 强转折性的词
强转折的词主要包括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。另一方面，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我们阅读的重点。特别是如果这种词出现在一段话的中前部，那么此句多半是整段话的论点，也就是整段的主题句。
需要注意的是，像although, though, despite, in spite of, albeit, 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 shareholders can demand more accountability. But when it comes right down to it, making sure a company is operating well is really an inside job. That’s where internal auditing comes in. It doesn’t sound glamorous, but it’s an expanding field beckoning to people with a lot of pent up we-can-do-better energy. Internal auditors keep an eye on a company’s “controls”-not just financial systems, but all sorts of functions designed to make the business run smoothly and protect the interests of shareholders.
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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 entirely by NASA. One was for International Flavors & Fragrances (IFF), which extracted the smell of a rose in space and was back seeking new scents. 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?
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B. 表重要性的结构
Are Americans a nation of frivolous divorcers who selfishly pursue the bluebird of happiness, oblivious to their children’s needs? Divorce opponents like Judith Wallerstein seem to think most parents see divorce as a marvelous opportunity for the whole family. How immature do they think people are ?All over America, unhappy spouses lie awake at night wondering if they and their kids can afford divorce financially, socially, emotionally. Where will they live, how will they pay the bills, will the kids fall apart, will there be a custody battle, what will their families say? The very fact that so many people leave their marriage for a future with so many pitfalls proves that divorce is anything but a whim. Most people I know who split up (not to mention my ex and me) spent years working up to it.
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The truth is that the economic boost from spinoffs, is untraceable. The Berlei bra, for instance, uses a Dupont material called CoolMax, which was derived from a fabric developed to improve thermal clothing by Outlast Technologies in collaboration with NASA’s Johnson Space Center. The proportion of Berlei bra sales accurately described as a NASA “spinoff” is anyone’s guess, but critics say returns can’t even come close to covering the cost of a shuttle flight.
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“The very fact that”这样的结构通常用来提示重要内容的出现。所以当类似的结构出现在段落首末位置的时候，该句极有可能是全段的主题句，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. 表示人物观点结论性的词:
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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 metropolitan 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,
