not true unless 到底是归纳还是假设由og-104想到的

104. Spending on research and development by United States businesses for 1984 showed an increase of about 8 percent over the 1983 level. This increase actually continued a downward trend evident since 1981 – when outlays for research and development increased 16.4 percent over 1980 spending. Clearly, the 25 percent tax
credit enacted by Congress in 1981, which was intended to promote spending on research and development, did little or nothing to stimulate such spending.
The conclusion of the argument above cannot be true unless which of the following is true?
(A) Business spending on research and development is usually directly proportional to business profits.
(B) Business spending for research and development in 1985 could not increase by more than 8.3%.
(C) Had the 1981 tax credit been set higher than 25%, business spending for research and development after
1981 would have increased more than it did.
(D) In the absence of the 25% tax credit, business spending for research and development after 1981 would not
have been substantially lower than it was.
(E) Tax credits market for specific investments are rarely effective in inducing businesses to make those investments

答案d

首先对于答案我并没有疑问，原来对e产生了一些疑问，后来看到网友提到specific investments比原来的research and development 的范围要广时明白了e的错误之处。

对于这道题我在看og解释的时候产生许多疑问，看了一下大家的发言也没有解我心中疑惑。

其中最关键的是该题是一道归纳还是假设呢，看解释之前这类题我基本是按假设作，当然了假设题按归纳做法似乎有些也有些道理，但看完解释后我感觉这题似乎是归纳。

首先看题干：题干说

The conclusion of the argument above cannot be true unless which of the following is true?

Unless = if not

如果下面的答案不对，那么结论也不对！

我们对该句话取逆否命题，也就是说结论对，则下面的答案也对，这不就是归纳吗？

事实上我们看og的部分解释也是按照归纳的解法给我们解释这道题的

Thus choice D must be true for the conclusion to be true and is the best answer.

(感觉像是一个假设)

Since a tax credit generally improves business profits, if the conclusion is true choice
A is unlikely to be true.。（这好像是说这是归纳）

狒狒说 not true unless 是假设的题型（诉诸权威），我在这里跳出来说这个是归纳实在是不合时宜亚！

便是如此，心中惑仍不能解。

记忆中好像nn们说假设题按归纳做也是可以的，感觉这也是可以理解的，因为归纳出的东西总是支持原文的，哈哈跑题了，大家还是帮我看看这道题是归纳还是假设吧！

我不同意你的观点，因为原命题的否命题不是原命题的互为充分必要条件

我认为原命题的逆否命题应该是

  Which of the following is true, if the conclusion of the argument above  is true?

Not A, unless B 应该是A-->B呀

还请批评指正  

haha 既然是bible说的，我还是得相信呀，虽然我不是特别的信服

不过有一点p200002还是给了我很大帮助的，那就是

从文中的conclusion推出assumption也是一种解题的方法，比如此题文中的结论是tax credit没用，我们可以推出来

没有tax credit，那些 investment也不会lower.

这种解题方法在多大程度上有效还请nn们赐教！

比如说 A --> B, B--->C, 那么A-->C，notC--> not A等等这些归纳出的答案 是否可以作为assumption的选项呢？
再次谢谢p200002的解释！

如果快要考试了，能选出正确答案是最重要的吧，这些考完再继续讨论不迟哦

对于这道题是假设还是归纳，我偏向于后者。也就是lawyer所说的MUST BE TRUE题。理由如下：

1.原问题的逆否问题，如楼主所说，是if the conclusion is true，which of the following must be true？

2.P200002所提供的解说中说到：Hence, the answer you select as correct must contain a statement that the author relies upon and is fully committed to in the argument.
这就说明，假设不但需要MUST BE TRUE，而且必须是结论所依据的东西。即使是后面的例句中有：The conclusion cited does not follow unless 和本题的问题非常相似，但个人认为follow和true还是有一定区别的。follow表示结论是由以下答案所推出，true却未必。
本题的结论并不是根据正确答案C所推出的。没有C，结论也能推出来。但是有了这个结论，C必然是正确的。所以应该是MUST BE TRUE题。

不知道大家有没有觉得，定义本题为MUST BE TRUE比定义为假设更容易找到答案。

不知道以上理解对否，请大家指教。

补充一个相似的题目：OG-122

When people evade income taxes by not declaring taxable income, a vicious cycle results. Tax evasion forces lawmakers to raise income tax rates, which causes the tax burden on nonevading taxpayers to become heavier. This, in turn, encourages even more taxpayers to evade income taxes by hiding taxable income.

The vicious cycle described above could not result unless which of the following were true?

(A) An increase in tax rates tends to function as an incentive for taxpayers to try to increase their pretax incomes.

(B) Some methods for detecting tax evaders, and thus recovering some tax revenue lost through evasion, bring in more than they cost, but their success rate varies from years to year.

(C) When lawmakers establish income tax rates in order to generate a certain level of revenue, they do not allow adequately for revenue that will be lost through evasion.

(D) No one who routinely hides some taxable income can be induced by a lowering of tax rates to stop hiding such income unless fines for evaders are raised at the same time.

(E) Taxpayers do not differ from each other with respect to the rate of taxation that will cause them to evade taxes.

122.

For tax evasion to force a raise in income tax rates it must be true that tax evasion causes actual tax revenues to fall short of revenue needs. This is the situation that choice C describes; choice C is therefore the best answer.

None of the other choices states a requirement for the vicious cycle to result. Increasing in pretax incomes (income A) would tend to work against perpetuation of the cycle. Success at catching tax evaders (choice B) should likewise have an inhibiting effect. Choice D describes how problems in breaking existing habits of tax evasion might be overcome. Choice E essentially denies that raising the tax rate in response to some tax evasion could cause additional tax-payers to evade taxes.

该题是假设毫无疑问

1。归纳题的逻辑思维是从原文到选项，就是说从原文得到选项，典型的是MUST BE TRUE 和MAIN IDEA题型。而演绎题型是选项对原文的推理产生作用，就像假设，是某个选项对原文起作用，就是说原文的结论依赖选项，选项不是从原文得出的，是作用原文的。

2。具体该题，问题问的是原文结论真实否依赖哪个选项，是选项对原文起作用。