托福TPO 9 听力Lecture第2篇第5题_Why does the professor mention shrub expansion into other environments, such as semiarid grasslands?

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题目

Why does the professor mention shrub expansion into other environments, such as semiarid grasslands?

To suggest that new shrubland may not convert back to tundra.

To explain how shrubland can expand in warm climate.

To cite a similarity between the types of shrubs in semiarid grassland and tundra environments.

To explain how a biological loop can cause shrub expansion.

题目解析

题目对应音频：Female student: I mean maybe the shrubs will be abundant for a few years, and then it'll change back to tundra. Prof: Well, shrub expansion has occurred in other environments, like semiarid grassland, and tall grass prairies. And shrub expansion in these environments does seem to persist.... Once is established, shrub land thrives.... 根据对话得知，女生说灌木林地可能会变回苔原，教授没有对此进行明确解答，而是举反例说其它环境中已经发生了灌木扩张现象，这种现象似乎是持续的，灌木一旦扎根，灌木林地就会茁壮成长。所以教授是通过这个例子说明灌木林地可能不会变回苔原，A 选项正确。

答案: A

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