Reading Comprehension

试题详情

文章:

    Over the last 150 years, large stretches of salmon habitat have been eliminated by human activity: mining, livestock grazing, timber harvesting, and agriculture as well as recreational and urban development. The numerical effect is obvious: there are fewer salmon in degraded regions than in pristine ones; however, habitat loss also has the potential to reduce genetic diversity. This is most evident in cases where it results in the extinction of entire salmon populations. Indeed, most analysts believe that some kind of environmental degradation underlies the demise of many extinct salmon populations. Although some rivers have been recolonized, the unique genes of the original populations have been lost.

    Large-scale disturbances in one locale also have the potential to alter the genetic structure of populations in neighboring areas, even if those areas have pristine habitats. Why? Although the homing instinct of salmon to their natal stream is strong, a fraction of the fish returning from the sea(rarely more than 15 percent) stray and spawn in nearby streams. Low levels of straying are crucial, since the process provides a source of novel genes and a mechanism by which a location can be repopulated should the fish there disappear. Yet high rates of straying can be problematic because misdirected fish may interbreed with the existing stock to such a degree that any local adaptations that are present become diluted. Straying rates remain relatively low when environmental conditions are stable, but can increase dramatically when streams suffer severe disturbance. The 1980 volcanic eruption of Mount Saint Helens, for example, sent mud and debris into several tributaries of the Columbia River. For the next couple of years, steelhead trout (a species included among the salmonids) returning from the sea to spawn were forced to find alternative streams. As a consequence, their rates of straying, initially 16 percent, rose to more than 40 percent overall.

    Although no one has quantified changes in the rate of straying as a result of the disturbances caused by humans, there is no reason to suspect that the effect would be qualitatively different than what was seen in the aftermath of the Mount Saint Helens eruption. Such a dramatic increase in straying from damaged areas to more pristine streams results in substantial gene flow, which can in turn lower the overall fitness of subsequent generations.

题目:

The primary purpose of the passage is to

选项:

A、argue against a conventional explanation for the extinction of certain salmon populations and suggest an alternative
B、correct a common misunderstanding about the behavior of salmon in response to environmental degradation caused by human activity
C、compare the effects of human activity on salmon populations with the effects of natural disturbances on salmon populations
D、differentiate the particular effects of various human activities on salmon habitats
E、describe how environmental degradation can cause changes in salmon populations that extend beyond a numerical reduction

答案:

E

提问:

错选D 知道第一段是说human activity, 第二段是说disturbances 没细读感觉也可能是human activity的一种?所以选了D . E选项的environmental degraduation只在第二段出现过 所以觉得选项可能表述的只是文章片面的内容无法成为主旨题答案 多谢老师解答
评分: 0
浏览: 117

提问:

阅读C中虽然有比较不爽,但是原文明明具体讲过这个比较这样也不好吗? 是不是这样理解,因为E中出现的信息在C中都出现过,所以E的出错概率低点? 请老师指点
评分: 0
浏览: 107

提问:

我听了老师的录音 觉得在看文章脉络的方面 我存在着一个显著问题 其实第二段的观点句 就是 二段第一句 可我在当时读脉络的时候,基本上除了第二段最后面的那个例子没读 其他的句子都读了。 因为,当时看这些句子 看起来都像判断句 有可能说明作者的观点 所以 就往下读一下,结果就读到段尾了 而且,不知是这么一篇文章会出现这种类似的情况。 我很想问问老师 我识别 观点句子的 方法是不是有问题? 到底应该怎样识别观点句呢??? 谢谢
评分: 0
浏览: 94

提问:

请老师讲解下。
评分: 0
浏览: 93

提问:

错选D 知道第一段是说human activity, 第二段是说disturbances 没细读感觉也可能是human activity的一种?所以选了D . E选项的environmental degraduation只在第二段出现过 所以觉得选项可能表述的只是文章片面的内容无法成为主旨题答案 多谢老师解答
评分: 0
浏览: 117

提问:

阅读C中虽然有比较不爽,但是原文明明具体讲过这个比较这样也不好吗? 是不是这样理解,因为E中出现的信息在C中都出现过,所以E的出错概率低点? 请老师指点
评分: 0
浏览: 107

提问:

我听了老师的录音 觉得在看文章脉络的方面 我存在着一个显著问题 其实第二段的观点句 就是 二段第一句 可我在当时读脉络的时候,基本上除了第二段最后面的那个例子没读 其他的句子都读了。 因为,当时看这些句子 看起来都像判断句 有可能说明作者的观点 所以 就往下读一下,结果就读到段尾了 而且,不知是这么一篇文章会出现这种类似的情况。 我很想问问老师 我识别 观点句子的 方法是不是有问题? 到底应该怎样识别观点句呢??? 谢谢
评分: 0
浏览: 94

提问:

请老师讲解下。
评分: 0
浏览: 93
点我领取
免费专项课程
在线咨询