侦探小说中，解决事件的关键通常是“细节”，侦探们在案发现场随身携带着放大镜，调查细节的时候连窗框下的微尘都不放过，这样的方法应用到托福听力中，对解决疑难杂题也会很有效果，据朗阁海外考试研究中心的老师观察发现，在托福听力中，需要同学们拿好放大镜观察的细节是——信号词。
 

　　说到托福听力当中的信号词，同学们应该并不陌生，大多数同学都能够如数家珍地列举出一系列，比如actually、especially、most important、interesting等等。但是，往往大家会忽略另一个非常重要的小词problem, 下面我们就以两篇TPO真题来谈一谈这个信号词在托福听力中的重要性。

　　首先我们来看看TPO 17 Lecture 1, 这篇关于prehistoric art的托福听力文章中主要围绕鉴别一个雕塑Lady with the Hood的年代展开，文章是典型的总分结构，通过分别介绍三种鉴别艺术品年代的方式，讲述了这些鉴定方式的缺陷是什么。而文章中也有多道题涉及到探测技术的缺陷这个知识点。

　　例如在介绍第一种technique时，先解释了什么是stratigraphy, 即利用地层去确定文物的年代，这种技术的宗旨是the oldest layers are at the lowest level. 紧接着一个转折就提到了这种技术的缺陷:

　　But this only works if the site hasn’t been touched, and the layers are intact. A problem with this dating method is that an object could have been carried around, used for several generations before it was discarded. So it might be much older than the layer or even the site where it was found.
 

　　所以在转折信号词之后提到第一个缺陷是必须要在完整未被破坏的底层，另外一个非常明显的信号就是problem之后提到这种技术有个很大的问题就是it might be much older than the layer or even the site where it was found。而这个出题点在第二题According to the professor, when might stratigraphy provide misleading information about a portable object?就有考察到，显然答案应该是When the object is older than the site at which it was found.

　　而这篇托福听力讲座的第三题问题是What are two disadvantages of radiocarbon dating? Click on 2 answers, 考察的仍然是利用碳的放射性探测雕塑会有什么缺陷。托福听力原文当中的表达是这样的:

　　So it turns out that radiocarbon dating works for a lot of prehistoric art. But again there’s a problem. This technique destroys what it analyzes, so you have to chip off bits of the object for testing. Obviously we are reluctant to do that in some cases. And apart from that, there’s another problems. The date tells you the age of the material, say, a bone or a tree the object is made from, but not the date when the artist actually created it. So, with radiocarbon dating, we get the maximum possible age for the object, but it could be younger.
 

　　在托福听力文中转折之后直接用problem引出了这个技术的缺陷是会破坏艺术品，另外用And apart from that引出另一个缺陷是we get the maximum possible age for the object, but it could be younger, 所以由problem引出的两个并列信息点告诉我们此题正确答案应为It causes damage to the material being analyzed.和It cannot prove when a piece of art was made.

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