阅读材料：
In the United States, it had been common practice since the late 1960s not to suppress natural forest fires. The let it burn policy assumed that forest fires would burn themselves out quickly, without causing much damage. However, in the summer of 1988, forest fires in Yellowstone, the most famous national park in the country, burned for more than two months and spread over a huge area, encompassing more than 800,000 acres. Because of the large scale of the damage, many people called for replacing the let it burn policy with a policy of extinguishing forest fires as soon as they appeared. Three kinds of damage caused by the let it burn policy were emphasized by critics of the policy.
在美国，从1960年代末开始就非常普遍地对森林大火采取不扑灭的策略。这种随它燃烧的策略认为森林大火可以在不造成太多损失的情况下迅速燃烧完。然后，1988年发生在美国最出名的黄石国家公园的森林大火却整整燃烧了两个月，蔓延了80万英亩。鉴于这次造成的巨大损失，很多人主张取消随它燃烧的策略，转而开始全力扑灭森林大火的策略。评论家们提供了三个由随它燃烧策略造成的损害来支持自己的观点。
First, Yellowstone fires cause tremendous damage to the parks trees and other vegetation. When the fires finally died out, nearly one third of Yellowstones land had been scorched. Trees were charred and blackened from flames and smoke. Smaller plants were entirely incinerated. What had been a national treasure now seemed like a devastated wasteland.
首先，黄石大火给公园里的树木以及其他植物造成了巨大的损失。当火燃尽的时候，黄石公园接近三分之一的面积已成焦土。火焰烧焦树木，浓烟熏黑树木。小型植物则被彻底烧成灰烬。当看到宝贵的国家财富成为一片荒地的时候，会是何种感觉？
Second, the park wildlife was affected as well. Large animals like deer and elk were seen fleeing the fire. Many smaller species were probably unable to escape. There was also concern than the destruction of habitats and the disruption of food chains would make it impossible for the animals that survived the fire to return.
第二，公园的野生动物也遭到了伤害。像鹿或者麋鹿这些大型动物在火灾中都逃脱了，但是很多小型动物却不能逃脱。同时，大火还破坏了动物的栖息地并打乱了食物链，这使得当或在结束之后，逃离的动物也无法回来栖息于此。
Third, the fires compromised the value of the park as a tourist attraction, which in turn had negative consequences for the local economy. With several thousand acres of the park engulfed in flames, the tourist season was cut short, and a large number of visitors decided to stay away. Of course, local businesses that depended on park visitors suffered as a result.
第三，火灾会降低公园对游客的吸引力，进而对当地的经济造成不良的影响。由于数千英亩的土地被火焰吞没，旅游旺季缩短了，而很多游客都会选择放弃游览黄石公园。当地的经济对于旅游业依赖很大，自然会受到负面影响。
阅读部分需要提取的观点是：
- Main point: 专家主张废除随它燃烧的策略
- Sub point 1: 会对国家公园的植物造成伤害
- Sub point 2: 会对国家公园的动物造成伤害
- Sub point 3: 火灾会降低公园对游客的吸引力
听力材料：
Actually, fires are natural part of ecological cycle and their role is not just destructive but also creative. That is why the let it burn policy is fundamentally a good one, even if it sometimes causes fires of the 1988 Yellowstone fire. Lets look at what happened after 1988 fire.
事实上，森林大火是生态系统的组成部分，而且大火的角色不仅仅是破坏性的，同时也是建设性的。这就是为什么随它燃烧政策基本上是正确的，尽管它导致了1988年黄石大火。让我们看看1988大火之后发生了什么。
First, vegetation. As you might imagine, scorched areas were in time colonized by new plants. As a matter of fact, the plants in Yellowstone became more diverse because the fire created an opportunity for certain plants that could not grow otherwise. For example, areas where the trees have been destroyed by the fire could now be taken over by smaller plants that needed open and shaded space to grow. And another example, seeds of certain plants species wont germinate unless theyre exposed to very high levels of heat. So, those plants started appearing after the fire as well.
首先，对于植物来说。你们可以想到，那些烧焦的地方随着时间的发展都会被新的植物覆盖。而且事实上，因为大火给一些本来难以生长的种类得以发芽，黄石的植物因此变得更具多样性。比如，原来长满树木的地方因为火灾遭到破坏，但现在那里长满了需要开阔而阴凉空间的小型植物。另一个例子是，一些植物的种子只有经受过非常高的温度之后才能够发芽。所以，这些植物会在大火之后开始生长。
Its a similar story with the animals. Not only did their populations recover, but the fire also created new opportunities. For instance, the small plants that replaced trees after the fire created an ideal habitat for certain small animals like rabbits and hares. And when rabbits and hares started thriving, so did some predators that depended on them for food. So, certain food chains actually became stronger after the fire than they were before.
动物的情况也类似。不但动物的数量会逐步回复，而且大火会给动物的生长带来新的机会。比如，那些在火灾之后取代原有树木的小型植物给一些小型动物提供了极佳的栖息地，比如兔子。当兔子的数量开始变多，那么以它们为食的捕食者的数量也会增加。所以，大火过后，相应的食物链会变得比之前更加稳定。
And last, fires like 1988 Yellowstone fire would be a problem for tourism if they happened every year. But they dont. It was a very unusual combination of factors that year, low rainfall, unusually strong winds, accumulation of dry undergrowth that caused fire to be so massive. This combination has not occurred since and Yellowstone has not seen such a fire since 1988. Visitors came back to the park next year and each year after that.
最后，只要1988年的黄石大火不是每年都发生，那么就不会对旅游业造成巨大问题。而事实上，也确实不会每年发生。大火的发生是在那一年诸多因素和偶然的相互作用。比如，降水少、罕见的大风，以及干燥的低层植被的聚集导致了那次大火规模空前。但是这些因素没有再次聚合，而黄石公园自1988年开始也没有出现过这样规模的火灾。游客在大火第二年的时候就会恢复，而且这种趋势会保持下去。
听力部分需要提取的观点是：
- Main point: 随它燃烧政策基本上是正确的
- Sub point 1: 植物会在大火之后恢复而且生长的更好
- Sub point 2: 动物也会在大火之后恢复，食物链会更加稳定
- Sub point 3: 只有每年都发生火灾才会影响当地旅游业，但是从1988年后再也没有发生