请教LSAT－12－IV－21,23

joywzy

21. When the supply of a given resource dwindles, alternative technologies allowing the use of different resources develop, and demand for the resource that was in short supply naturally declines. Then the existing supplies of that resource satisfy whatever demand remains. Among the once-dwindling resources that are now in more than adequate supply are flint for arrowheads, trees usable for schooner masts, and good mules. Because new technologies constantly replace old ones, we can never run out of important natural resources.

Which one of the following, if true, most seriously undermines the conclusion?

(A) The masts and hulls of some sailing ships built today are still made of wood.

(B) There are considerably fewer mules today than there were 100 years ago.

(C) The cost of some new technologies is often so high that the companies developing them might actually lose money at first.

(D) Dwindling supplies of a natural resource often result in that resource's costing more to use.

(E) The biological requirements for substances like clean air and clean water are unaffected by technological change.

答案：E，我选了C，为什么E是削弱呢？

23. A study of adults who suffer from migraine headaches revealed that a significant proportion of the study participants suffer from a complex syndrome characterized by a set of three symptoms. Those who suffer from the syndrome experienced excessive anxiety during early childhood. As adolescents, these people began experiencing migraine headaches. As these people approached the age of 20, they also began to experience recurring bouts of depression. Since this pattern is invariant always with excessive anxiety at its beginning, it follows .hat excessive anxiety in childhood is one of the causes of migraine headaches and depression in later life.

The reasoning m the argument is vulnerable to criticism on which one of the following grounds'?

(A) It does not specify the proportion of those in the general population who suffer from the syndrome.

(8) It fails to rule out the possibility that ail of the characteristic symptoms of the syndrome have a common cause.

(C) It makes a generalization that is inconsistent with the evidence.

(D) it fails to demonstrate that the people who participated in the study are representative of migraine sufferers.

(E) It does not establish why the study of migraine sufferers was restricted to adult participants.

答案：B，我选了D

谢谢。

mindfree

Joy,

My suggestion to you is not to do more exercise, but think more and understand the problem. After reading your recent posts, I think you are still making the same mistakes as you did before. In another word, you have not learned from your past. It sounds cruel but you must realize it.

For example, 1T is a typical GMAT CR. Your mistake is also typical in problems we discussed before. You need to know what is the premise and what is the conclusion.

P: If technology make demand for natural resources in short supply dwindle
C: we will not run out of NR

Cost is not a consideration here, unless it is a prohibitive factor.

Let me give you another example: Solar power technology is developed, we will rely on crude oil less and less. Here cost is not a factor. No matter it is expensive or cheap to use solar power, the reasoning holds. But if I argue that solar energy is prohibitively expensive and will be so for a long time, then the reasoning is flawed, as the cost renders the technology useless for a long time.

BTW, if the reasoning is that: "if we use solar energy soly, we do not need crude oil", then cost and any other factor that make solar energy ununsable cannot weaken the argument. The reason is that the argument assumes that solar energy is usable. So it is irrelevant if it is usable in reality.

2. The study is not on migraine. And the conclusion has nothing to do with whether these people are typical migraine sufferers or not. In another word, they do not have to represent migraine sufferers.

For example, people who hated study when young hated word when older, then hated life when even older. So the conclusion is that hate-->hate-->hate. It does not matter if there people who hated work represent all the people who hated work. It is irrelevant.

B is typical answer. You think about it...

joywzy

mindfree,

非常感谢你的帮助和提醒，谢谢你!我下决心这两天将以前的提问的贴子重新看一遍，希望能发现问题，及时改进!

T2，

P： this pattern is invariant always with excessive anxiety at its beginning,
C： it follows .hat excessive anxiety in childhood is one of the causes of migraine headaches and depression in later life.

削弱：只有共同的原因。

T1，

P: If technology make demand for natural resources in short supply dwindle
C: we will not run out of NR

削弱：有些因素不受technology的影响。

另外，关于cost 是否相关的问题，我还是有点疑问：

如果C说：

The cost of most new technologies is often so high that the companies developing them will definitely lose money .

把technologies的问题说得比较严重，是不是就是削弱了，因为原先的C说得some, at first,不严重，并没有削弱。

我这样理解对吗？

mindfree, 最近做LSAT，我削弱题的错误占了错误率的一半。感觉到一个问题就是没有分清前提和结论，另外还有一些的选项判断不清是不是无关，经常把他们当作他因了。我确实需要重新回顾总结了。

谢谢。

[此贴子已经被作者于2003-6-15 17:49:26编辑过]

perfection

以下是引用joywzy在2003-6-15 17:43:00的发言：
mindfree,

另外，关于cost 是否相关的问题，我还是有点疑问：

如果C说：

The cost of most new technologies is often so high that the companies developing them will definitely lose money .

把technologies的问题说得比较严重，是不是就是削弱了，因为原先的C说得some, at first,不严重，并没有削弱。

我这样理解对吗？

mindfree, 最近做LSAT，我削弱题的错误占了错误率的一半。感觉到一个问题就是没有分清前提和结论，另外还有一些的选项判断不清是不是无关，经常把他们当作他因了。我确实需要重新回顾总结了。

谢谢。

  

[此贴子已经被作者于2003-6-15 17:49:26编辑过]

我认为即使把cost说得很严重，也不是一个很好的weaken.除非我们能从中得到一个额外的假设：企业资金的流失会阻碍或者延缓新技术的实现。

逻辑题中需要一定的想象，但不能过多，也不能额外增加假设。

另外最好的答案是排出来，不是推出来的。在做题过程中，不要去想那个答案为什么正确，要去找答案中的错误。逐步排除和比较。也许错误就减少了。

albert

我觉得这里COST还是有关的。。
原文：
Because new technologies constantly replace old ones, we can never run out of important natural resources.

new technologies constantly replace old ones是原文的前提，也是假设。

削弱原文可以通过否定前提来。。也就是说明: new technologies constantly replace old ones不成立。。有很多因素可以做到。。如COST不可行，技术根本无法达到,政治伦理上无法实现。。等等。。

所以我觉得C的问题主要出在几个词上： SOME， AT FIRST。。因为即使SOME 不行，只要有行的就可以了。

E的WEAKEN是通过技术根本无法达到来否定前提的。。

所以，我认为我们不需要“企业资金的流失会阻碍或者延缓新技术的实现。
”的assumption...因为COMMON SENSE是如果COST 太大，LOST MONEY的事情企业是不会干的。

一家之言，欢迎讨论。。我觉得这道题目挺有代表性的。。我们应该多多讨论一些有代表性的题目，从中明白为什么错，为什么对。。这样我们的水平都会上升的。

[此贴子已经被作者于2003-6-16 0:12:02编辑过]

fredshen

For 12-4-21, An old debate, I'd like to chip in, in case other people get confused.

In weaken question,  LSAT is not as interested in weakening the premise as weakenig the conclusion. The cost issue here at best is to weaken the premise that new technology cannot constantly replace old ones. But this is hardly a logic excersie. We have to accept the premise. Even given the validty of this line reasoning, the premise is still prediction in nature. Something can ..., it's hard to weaken this prediction to say this thing has limitation so that it cant. This is not the real issue here.

The real issue here is demand and supply, that new technology will dwindle demand for old resources. It ignores that the demand for evironmental resources are uneffected, and it can be run out. This line of thiking is classical debate between envrionment preservationaists and progressionists.