听力材料：

　　The cane toad won’t be as easy to get rid of as the reading suggests. The measures proposed by the reading are likely either to be unsuccessful or to cause unwanted environmental damage.
　　蔗蜍不会像阅读部分说的那么容易出去的。阅读部分提供的观点不但是不会奏效，甚至会对环境造成损害。

　　First of all, a national fence probably won’t stop the spread of the toad. That’s because young toads and toad eggs are found in rivers and streams. No matter where the fence is located, at some point there will be rivers or steams flowing from one side to the other. These waterways will be able to carry the young toads and their eggs to the other side. Since it’s only necessary for a few young toads or eggs to get though the fence in order to establish population on the other side, the fence is unlikely to be effective.
　　首先，一个全国范围内的围栏不会阻止蔗蜍的蔓延。这是因为蝌蚪和蔗蜍卵是生活在河水和溪流中的。不管围栏怎么安排，总会有跨过河流和小溪的地方。在这些地方，流水可以越过围栏。蝌蚪和蔗蜍卵可以通过这些水流穿过围栏。只要有很小数量的蝌蚪和蔗蜍穿过围栏，它们就可以建立起一个种群。所以，这种围栏的方法是无效的。

　　Secondly, a massive group of volunteers could have success trapping and destroying toads. But it’s likely that these untrained volunteers would inadvertently destroy many of Australia’s native frogs some of which are endangered. It’s not always easy to tell the cane toad apart from native frogs especially when it’s young.
　　第二，人数众多的志愿者队伍的确可以抓住和消灭蔗蜍。但是这些没有经过训练的志愿者很可能会无意间杀死很多澳大利亚原产的青蛙，而其中的一些已经是濒危物种的。蔗蜍和澳大利亚原产青蛙并不容易区分，尤其是在它们都是幼体的时候。

　　Third, using the virus is a bad idea because it could have terrible consequences for cane toads in their original habitat in Central and South America. You might be wondering how can virus released in Australia cause harm in the Americas. Well, Australian reptiles and amphibians are often transported to other continents by researchers or pet collectors for example. Once the animals infected by the virus reach Central and South American, the virus will attack the native cane toads and devastate their populations. That would be an ecological disaster because in the Americans cane toads are a native species and a vital part of the ecosystem. So if they are eliminated the whole ecosystem will suffer.
　　第三，病毒可能会对蔗蜍原产的中南美洲的生态环境造成严重的破坏，所以使用病毒也是一个坏主意。你们可能很好奇为什么投放在澳大利亚的病毒会破换美洲的环境。恩，研究者或者宠物饲养者常常会被澳大利亚的爬行动物和两栖类动物带到其他的大洲。一旦感染此病毒的动物被带到了中南美洲，那么这种病毒就会感染当地的蔗蜍，使得其数量锐减。因为蔗蜍在美洲是原生物种，是生态系统的重要组成部分，所以其数量锐减将会是生态灾难。所以，如果蔗蜍灭绝了，那么美洲的生态系统也会受到破坏。

　　听力部分需要提取的观点是：
　　- Main point: 三个方法是无效甚至只有害的。
　　- Sub point 1: 蔗蜍的蝌蚪和卵可以通过流水穿过围栏，方法无效。
　　- Sub point 2: 尽管志愿者可以抓到蔗蜍，但是可能会错抓当地濒危的原产青蛙。
　　- Sub point 3: 使用病毒可能会破坏蔗蜍原产地中南美洲的生态平衡。