Questions are based on the following passage. There can be few more d-考呗网

英语六级

单选题Questions are based on the following passage.
There can be few more depressing stories in the entire history of man's exploitation of nature than the destruction of the unfortunate great whales. The whales have not only suffered untold cruelty but now face total extermination (灭绝.. Already entire populations have been wiped out, and the only reason why no species has yet been finished off is due to the vastness and inaccessibility (难达到. of the oceans; a pocket or two somewhere has always managed to escape. How ironic if biological extinction were to complete the job.
The basic rule of extinction is very simple: it occurs when a species mortality is continually greater than its recruitment. There are though, some very special additional factors in the case of whales.
Man does not actually have to kill the last whales of a species with his own hands, as it were, to cause its disappearance. Biological extinction will quickly follow the end of commercial whaling, should that end be due to a shortage of raw material, i.e. of whales. Whalers have long sought to defend their wretched trade by insisting that whales are automatically protected: as soon as they become rare, and therefore uneconomic to pursue, man will have no choice but to stop the hunting. That is a very nice theory, but it is the theory of an accountant and not of a biologist; only an accountant could apply commercial economics to complex biological systems. The reasons for its absurdity are many and varied. In the case of whaling it can be summed up in the following way.
When the stock has been reduced below a critical level, a natural, possibly unstoppable downward spiral begins because of three main factors. First, the animals lucky enough to survive the slaughter will be too scattered to locate one another owning to the vastness of the oceans. Secondly, whales being sociable animals probably need the stimulus of size able gatherings to induce reproductive behavior. It is quite likely that two individuals meeting through chance will not be compatible. (They can hardly be expected to be aware of their own rarity or to realize any need for adjusting their natural inclinations. . This is especially so with polygamous (一夫多妻的. species like the Sperm Whale. Thirdly, and perhaps most important in the long term, even allowing that the whales might still be able to band together in socially acceptable groups (thanks to their undeniably excellent communicative systems., there is a real danger, possibly even a probability, that the whales' gene pools would by then have sunk so low as to be biologically unviable. That is to say, the characteristics possessed by the original population would be whittled down to those characters possessed by only the few remaining individuals. The result of such a biological disaster is inbreeding (近亲繁殖., less ability to adapt to new conditions, and less individual variety. Three words can sum it up: permanent biological extinction. The future . "hopes" of these animals are further discussed in the final chapter.
According to the passage, the extinction of whales is caused by

A． man's continuous evolution process
B． people's excessive hunting and killing
C． the changing living conditions in nature
D． the demand from a booming economy

参考答案：B进入在线模考

【参考译文】
[51]在整个人类开发自然的历史上，很少有比大鲸鱼的不幸毁灭更令人沮丧的故事了。鲸鱼不仅承受了数不清的残酷行为，而且现在濒临灭绝。整个种群已经被消灭了，这个物种还没消失的唯一原因在于海洋浩瀚无边，人们难以达到深处。某些地方的一两只总能设法逃脱。如果生物灭绝要完成这项工作的话．
将是多么讽刺啊!
[52]物种灭绝的基本准则是很简单的：当一个物种的死亡率持续高于出生率时，灭绝就发生了。尽管如此，对于鲸鱼而言，却有一些很特别的额外因素。
从某种角度说，要使鲸鱼消失，人们并不需要实际上手刃这一物种的最后一条鲸鱼。如果商业捕鲸因为原材料，即鲸鱼的缺乏而停止的话，那么，鲸鱼的生物灭绝也就会迅速随之发生了。[53]长期以来，捕鲸者力图通过强调鲸鱼可以自动受保护来为他们卑鄙的勾当正名：鲸鱼一变得稀有，就没有捕捉的经济价值了，那么，人们除了停止捕鲸外别无选择。这是一个很不错的理论，但这是一住会计师的理论，而不是一位生物学家的理论；只有会计师能将商业经济学运用到复杂的生物系统中。导致其荒谬的原因多种多样。就鲸鱼而言，可以总结如下：
[54]当种群被降到临界水平之下时，由于以下三个主要原因，种群数量自然就会发生螺旋式下降，而且这或许是不可阻挡的。第一，[55]由于海洋的浩瀚性，幸免于屠杀的动物会变得分散，难以找到彼此。第二，鲸鱼是社交性的动物，要诱导它们的繁殖行为，很可能需要刺激它们大规模聚集在一起。[55]偶然相遇的两个个体很可能是丕能共处的。(我们几乎不能期待它们意识到自己的稀缺性或让它们意识到有必要调整自己的自然天性。.对于诸如抹香鲸这类一夫多妻的物种尤为如此。第三个原因，长期来看或许是最重要的原因在于，即使鲸鱼或许能够以可社交的组群聚集在一起(这得归功于它们无疑异常杰出的沟通系统.，也还很可能存在一个真正的风险，那就是，到时鲸鱼的基因库会过分缩小，以致从生物角度看无法维系该种群。也就是说，原有种群的特点将会被削弱，变为现存少量个体所拥有的特点。这种生物灾难的结果就是近亲繁殖，适应新环境的能力降低，个体多样性减少。可以这样来概括：持久性的生物灭绝。这些动物的未来“前景”会在最后一章深入讨论。
定位：根据题干中的信息词the extinction和whales定位到第一段第一句。
解析：该句意为：“在整个人类开发自然的历史上，很少有比大鲸鱼的不幸毁灭更令人沮丧的故事了。”由此可判断，鲸鱼的灭亡与人类对自然的开发，即捕杀活动存在因果关系。故B项与原文意思相符，为正确答案。题干中extinction与原文destruction对应。

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1What can we infer from the basic rule of extinction?

A． Whales die more than they are born each year.
B． Whales' reproductive ability remains a very low rate.
C． The species of whales is doomed to extinction.
D． Whales' death rate keeps an increasing trend.

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A． people's growing awareness of the balance between ecology and business
B． their theory which has been derived from life experiences
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3What will happen if whale numbers drop to a certain degree?

A． The number will bounce back at a certain point.
B． Whales begin to adapt to new living conditions.
C． The extinction of whales becomes unavoidable.
D． A biological disaster will come to the earth.

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