求教逻辑题答案

钰剑乘风UID：3279007

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.

我选B,网上各种答案都有不知哪一个正确。。。。

crazyrobinUID：2368627

这道题的premise是， massive volcanic eruptions和meteorites that shower down on Earth from space产生iridium，科学家发现65万年前地球上的iridium的含量很高（30倍），所以科学家推论是小行星撞击地球使得恐龙灭绝了

这个推理过程中2点，1，小行星撞击地球会导致产生大量iridium, 2,大量iridium会导致生物灭绝

第一点已经被文章证实了，第二点是推理必须的，答案选D

钰剑乘风UID：3279007

crazyrobin 发表于 2012-12-6 21:34
这道题的premise是， massive volcanic eruptions和meteorites that shower down on Earth from space产生i ...

2,大量iridium会导致生物灭绝
我不同意这点，这个不是他推理过程中必须的，小行星直接撞地球就会导致恐龙灭绝啊。

我选B的原因是他说产生大量iridium有两种情况，B的话就排除了第一种情况的可能，从而有力的支持了观点。

crazyrobinUID：2368627

钰剑乘风 发表于 2012-12-7 11:45
2,大量iridium会导致生物灭绝
我不同意这点，这个不是他推理过程中必须的，小行星直接撞地球就会导致恐龙 ...

我查了一下,有个论坛说官方的答案是B

解释：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.

crazyrobinUID：2368627

答案的解释里还是跳过了重要的推理，就是Iridium会使生物灭绝。如果你直接推理为小行星撞击地球使生物灭绝，那么最强有力的论证应该是Iridium不会使生物灭绝（这样火山爆发和小行星撞击地球所产生的Iridium都不会使生物灭绝，反而是第三方的因素，那么这个题就失去了推理的意义）

答案解释说是小行星撞击地球使得Iridium含量大量提高，所以导致生物灭绝，那么最重要的论证就是火山爆发（产生的Iridium）不会使生物灭绝。这样就可以解释通了。我之前的答案忽略了一个点。直接选了火山爆发。

钰剑乘风UID：3279007

crazyrobin 发表于 2012-12-7 12:18
答案的解释里还是跳过了重要的推理，就是Iridium会使生物灭绝。如果你直接推理为小行星撞击地球使生物灭绝， ...

多谢~！

EnolateUID：3283311

Ir在这里并不是使恐龙灭绝的原因，它只是做为一种证据来指向导致灭绝的元凶--火山喷发或者是陨石撞击

这两者能引起恐龙灭绝的因素并不是它们都使地表有大量的Ir，而是笼罩的天空久不散去的云雾遮蔽了阳光，使得地球的含氧量下降、气候变冷，火山喷发还会造成大气中有很多含硫的气体，污染空气
---不过这在题目里不重要。题干没有说Ir会导致灭绝，推理的时候不需要考虑这一点

我觉得楼主的推理已经够直接和切题了

麻倉枼UID：3376337

我还没看过，你看看有没有你的答案。。貌似你这个是在26套里面的

钰剑乘风UID：3279007

麻倉枼 发表于 2012-12-7 21:03
我还没看过，你看看有没有你的答案。。貌似你这个是在26套里面的

谢啦

四UID：3553123

我觉得这个题很诡异。。
题目并没有告诉我们80百万年前恐龙出现了没有啊= =

也许恐龙是70百万前出现的呢