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定位原文：
Professor: So I heard that your field work group ended up camping a few days longer than expected.
Student: Yeah, the bus broke down. It gave us time to gather more specimens from the lake to study in the lab, but unfortunately, it meant missing a day of classes, including the class when you described the requirements for the paper.
解析：学生先是解释了一下为什么错过教授的课，而课上教授是提到了论文要求，所以学生来找教授的主要目的是为了了解论文要求。选C。
Q19
正确答案：D
定位原文：
Professor: That brings back memories from my undergraduate days.
解析：教授听完学生的解释，说了一句“让我想到我没毕业的时候了”，说明他之前也经历过同样的事情，选D。
Q20
正确答案：B
定位原文：
Professor: So uh anyway, what I'm looking for is an ecological situation in which the solution causes a much greater problem than the original problem it was intended to solve. The example I gave in class was about cane toads in Australia. They were imported there in 1935 to control the grey-backed cane beetles that were destroying the sugarcane crop.
解析：学生缺席了教授的一节课，因此教授在这里简单介绍了他要求的论文内容，并且举了cane toads的例子用于解释他提到的概念。选B。
Q21
正确答案：A
定位原文：
Student: Well, I got the idea from a radio interview I heard. It was with an ecologist who claims that the greatest threat to the greatest number of species in the next 25 years is not global warming, as one would expect, but the cultivation of oil palm trees.
解析：学生是从一个广播采访中听到一个生物学家说：未来25年最大的威胁不是全球变暖，而是油棕榈树的种植。对应A选项。
Q22
正确答案：BDE
定位原文：
Student: Everybody thought it was a sure winner. It made a lot of sense both economically and environmentally. Here's a crop that's in high demand, easy to grow, and won't disrupt the ecosystem.
解析：学生提到大家都觉得种植油棕榈树能带来好处，因为这一作物的需求很大，很好种植，也不会破坏生态系统。分别对应BDE选项。
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