第一类信号词是一些并列词，比如：and, also, another, other, plus, not only… but also等;
例题：TPO15 - C2
3. What does the student need to do before he can use any rare books? Click on 2 answers.
a. Purchase a card
b. Obtain permission
c. Put on gloves
d. Try interlibrary loan service
对应原文：You need to get special permission to access them, and then you have to wear gloves to handle
解析：老师对学生说要使用rare books首先必须得到特殊的许可，咱们听到了permission这个单词，对应的是B这个选项;and then表示并列的词引导出第二个要求wear gloves，咱们又听到了gloves这个单词，对应的是C这个选项。所以答案是BC。
第二类信号词是一些数量词，比如：the first, the second等;
例题：TPO 24 - L4
2. How were scientists able to learn new information about Venus' surface? Click on 2 answers.
A. More powerful telescopes allowed astronomers to see more surface details.
B. Satellites were used to get radar images of Venus's surfaces.
C. Space modules sent photographs after landing on Venus.
D. A space probe was able to locate gaps among Venus' clouds.
对应原文：First of all, let me talk about how we have been able to get past those clouds. First, there were Soviet modules that landed directly on the surface and sent back some images of what was around them. Second, we did some radar imaging from satellites from above.
解析：教授说让我们来探讨如何穿过那些云层的，首先我们听到了第一个信号词first， 接着我们听到了modules这个单词，刚好对应的C选项;接下来我们听到了第二个信号词second，接着我们听到了radar imaging from satellites，radar这个单词对应的是B这个选项。所以答案是BC。
第三类信号词是一些名词：比如：factors, reasons, categories, elements, different kinds等;
例题：TPO7 - L4
4. What factors are involved in the amount of deformation a glacier undergoes? Click on 2 answers
A. The thickness of glacial ice
B. The hardness of glacial ice
C. The amount of water beneath the glacial ice
D. The temperature of the glacial ice
相应原文：Now, there are a couple of factors that affect the amount of deformation that takes place or the speed of the glacier's movement for example. Deformation is more likely to occur the thicker the ice is, because of the gravity of the weight of the ice. And temperature also plays a part here, in that cold ice does not move as easily as ice that is close to the melting point.
解析：在这道题目当中，教授先用a couple of factors这样的总分结构引入下面的分论点，然后说了2个影响冰川变形量的因素，以并列连接词also连接，第一个是the thicker the ice is, 第二个是temperature,所以答案应该是AD。