magoosh一片逻辑很绕的阅读 大家又觉得吗还是我太弱了

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One reason we are able to recognize speech, despite all the acoustic variation in the signal, and even in very difficult listening conditions, is that the speech situation contains a great deal of redundancy—more information than is strictly necessary to decode the message. There is, firstly, our general ability to make predictions about the nature of speech, based on our previous linguistic experience—our knowledge of the speakers, subject matter, language, and so on. But in addition, the wide range of frequencies found in every signal presents us with far more information than we need in order to recognize what is being said. As a result, we are able to focus our auditory attention on just the relevant distinguishing features of the signal—features that have come to be known as acoustic cues.

What are these cues, and how can we prove their role in the perception of speech? It is not possible to obtain this information simply by carrying out an acoustic analysis of natural speech: this would tell us what acoustic information is present but not what features of the signal are actually used by listeners in order to identify speech sounds. The best an acoustic description can do is give us a rough idea as to what a cue might be. But to learn about listener’s perception, we need a different approach.

是篇短文，词汇不难看了好几遍还是晕的，3道题只能纯蒙。
The primary purpose of the passage is to

The first paragraph of the passage implies which of the following concerning sound and communication?

The main reason that the author of the passage discounts using a purely acoustic analysis to understand the way in which humans are able to recognize sounds is that

还有就是infer的题 如果有一个选项是原文的同义改写，能选吗？还是一定要选延伸的选项？总感觉更延伸的选项有种yy的成分在里面 - -