询问一道恐龙灭绝和行星撞地球(逻辑)题

yli161

原题是：Iridium, a hard, whitish metal similar to platinum, is extremely rare on Earth. Extremely high concentrations of iridium on Earth result
from only two scenarios: massive volcanic eruptions that release iridium from deep within the Earth and meteorites that shower down on Earth from space. When scientists found concentrations of iridium 30 times higher than normal in rock stratum from 65 million years
ago, they concluded that a massive meteor or comet hit the Earth and caused the massive extinction of the dinosaurs.

Which of the following, if true, most strongly supports the scientist’s conclusion?

A. Volcanoes massive enough to generate high concentrations of iridium are very rare.
B. Massive volcanic eruptions occurred frequently 80 million years ago.
C. Most scientists support the hypothesis that a cosmic impact wiped out the dinosaurs.
D. The massive extinction that occurred 70 million years ago killed not only the dinosaurs but also 70 percent of all life on Earth.
E. A comet struck the earth some 120 million years ago, but no widespread extinction occurred.


请问答案是什么？

yli161

一个外国网站上大家的答案众说纷纭，有人选A，有人选B，有人选C。但是有一个人给出一个类似标准答案：
Re: Iridium from meteors and comets: Need help [#permalink]
Sun May 22, 2011 10:08 pm
Here is the explanation provided by the guide:

Answer: B. This is a strengthen question. Its conclusion and premises are:
Premises: (1) Extremely high concentrations of iridium on Earth result from only two scenarios: massive volcanic eruptions that release iridium from deep within the Earth and meteorites that shower down on Earth from space. (2) Scientists found concentrations of iridium 30 times higher than normal in rock stratum from 65 million years ago.
Conclusion: A massive meteor or comet hit the Earth and caused the mass extinction of the dinosaurs.

According to the premises, there are two possible causes of high iridium levels. But the conclusion states that one of the causes—a meteor— was definitely the culprit. So the assumption must be that there was not a volcanic eruption that caused the extinction. Once again, you have a causal argument, but now you are going to strengthen it. In order to do so, you should look for answers that rule out other possible causes. Choice B strengthens the argument by showing that volcanic eruptions occurred frequently before the extinction, but the dinosaurs continued to live. Thus, it is unlikely that the extinction was caused by a volcano and more likely that a meteor caused it. Choice A doesn’t go far enough. Even if the volcanoes are rare, the extinction could have been caused by just one eruption. Choice C doesn’t strengthen the argument. Other scientists’ support of the hypothesis doesn’t address the connection between the conclusion and the premise. Choice D has nothing to do with the argument, while choice E weakens the argument by indicating that a previous comet strike did not lead to an extinction.
_________________
Regards
Rahul


是否答案是B？

littlekii

我怎么觉得是A呢


如果是B的话    80M 之前大量的  MASSIVE V 会导致 I的增多 这不就 WEAKEN 了结论了吗

yli161

Choice B strengthens the argument by showing that volcanic eruptions occurred frequently before the extinction, but the dinosaurs continued to live. Thus, it is unlikely that the extinction was caused by a volcano and more likely that a meteor caused it. Choice A doesn’t go far enough. Even if the volcanoes are rare, the extinction could have been caused by just one eruption.

他给出解释：B选项：在恐龙灭绝前，火山喷发频繁发生，但是恐龙却继续存活。这样，恐龙的灭绝不可能由火山喷发引起，而更可能由陨石撞击地球引起。
                 A选项：即使火山喷发很少，但是恐龙还是可能因一次喷发而灭绝。


（我一开始也觉得是A选项，但是看了他的解释又犹豫了><）

bedrop

本来也觉得是a的
看了你的解释我觉得我被那个老外说服了。。。

Channery

A. Volcanoes massive enough to generate high concentrations of iridium are very rare.

是火山少，这个修饰语太长了，让人看成iridium少了，太具有欺骗性了！

novaleilei

表示一看就是选的B

jasondang

这道题选A。通常逻辑题，我们只要能证明或者否定它的假设，我们就能加强或否定它的结论。这道题的前提条件是concentrations of iridium 30 times higher than normal in rock stratum from 65 million years ago，那么作者推出结论的假设就是，这种high concentration 的iridium不是由火山爆发而是由彗星撞地球得来的。那么，我们如果可以找到一个能够证明这个假设的选项，那么就可以加强作者的结论。显而易见，答案是A，因为只有这个选项极大削弱了high concentration的iridium是火山爆发得来的可能性。B选项的问题在于，它与我们结论的假设无关，也就是说它没有考虑到iridium concetration的问题，虽然从另一个角度也说的过去（尽管我觉得80million 和 65million年代差的也挺久的），但是没有从根本上支持到作者的假设，所以不是最佳选项。

不如阿帕斯

我觉得如果按老外那么说，我们就还需要知道：80之前就有恐龙，它们经历80火山而不死。那不就违背ETS的不涉及专业知识？

才疏学浅，觉得选A

lxtbkl

是说80million年前火山常爆发，可能产生了很多的Ir,但即使这样，文中表明65million年前的Ir的含量还是比普通岩层中高出30倍，所以说岩层中的Ir的过高不是由于火山爆发形成的，而只可能是撞击形成的。当然如果80million年前火山常爆发形成不了Ir,不用说65million年前的Ir的含量异常肯定是由于撞击形成，因为高浓度Ir的形成文中表明只有2种途径。