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Morning, I’m AmyLee，glad to see you today!本听力材料来自于老托partb，partc，是公认实施有效的听写材料，对于上手托福时间不长的同学非常适合。我曾经一次短时间备考听力提高了7分也归功老托。希望大家和我一样一定要坚持下来噢。相信坚持学习的同学听力上都会有很大的飞跃！
No pain, no gain.我们的安排是这样的，第一遍用听力软件精听材料（建议做单句听写，听写的时候不要偷看我给的挖空题），然后按照我给的挖空题填关键词，回复后即可看到听力原文和文章精解，我将把难点和易错点one by one 分析给大家。
回复填空答案格式如下：1____2____3____...et.al.
I'm glad you brought up the question of our investigations into the ______of the Earth's interior. In fact, since this is the topic of your reading assignment for next time, let me spend these last few minutes of class talking about it. There were several important discoveries in the early part of this century that helped geologists develop a more accurate picture of the Earth's interior. The first key discovery had to do with ______ waves. Remember they are the ______caused by earthquakes. Well, scientists found that they traveled thousands of miles through the Earth's interior. This finding enabled geologists to study the inner parts of the Earth. You see, these studies revealed that these vibrations were of two types: ______ or P waves and ______ or S waves. And researchers found that P waves travel through both liquids and solids, while S waves travel only through solid matter. In 1906, a British geologist discovered that P waves slowed down at a certain depth but kept traveling deeper. On the other hand, S waves either disappeared or were reflected back, so he concluded that the depth marked the ______ between a solid ______ and a liquid ____. Three years later, another boundary was discovered, that between the mantle and the Earth's _____. There's still a lot to be learned about the Earth. For instance, geologists know that the core is hot. Evidence of this is the _____, ____that flows out of volcanoes. But we're still not sure what the source of the heat is.
