[求助]TT GWD-3-40

Q40:

For most people, the left half of the brain controls linguistic capabilities, but some people have their language centers in the right half.  When a language center of the brain is damaged, for example by a stroke, linguistic capabilities are impaired in some way.  Therefore, people who have suffered a serious stroke on the left side of the brain without suffering any such impairment must have their language centers in the right half.

Which of the following is an assumption on which the reasoning in the argument above depends?

1. No part of a person’s brain that is damaged by a stroke ever recovers.
2. Impairment of linguistic capabilities does not occur in people who have not suffered any damage to any language center of the brain.
3. Strokes tend to impair linguistic capabilities more severely than does any other cause of damage to language centers in the brain.
4. If there are language centers on the left side of the brain, any serious stroke affecting that side of the brain damages at least one of them.（D）

   E   It is impossible to determine which side of the brain contains a person’s language centers if the person has not suffered damage to either side of the brain.

Why D???

这题好像比较清楚。题目说，如果中风左脑的人，语言功能没有受到影响， 那语言中心一定在右脑。

如果中风在左脑->必定影响语言功能。为什么呢？D说出了前提。

D说明，至少中风左脑会影响语言中心的其中一个。

therefore后面的，就是绝对排除了语言中心在左脑，中风在左脑，也可能不影响语言功能的可能性。所以这里提到了右脑。就是说，要么语言中心在右脑，所以中风在左脑不影响语言功能；要么，语言中心在左脑，中分在左脑肯定会影响语言功能。

第一种情况已经被therefore后面的否定掉了。那么，第二种情况发生就必须是D，就是说语言中心在左脑，左脑中风肯定至少伤害到一个语言中心了，所以才会影响语言功能。

不知道说清楚了没有。其实这题就是倒过来顺过去的推。有点像数学里面A->B,否A->否B的意思。楼主再体会体会。

明白!也就是说therefore后面只是对前面说到的只要语言中心在左脑,且左脑受伤害,那么语言中心一定受伤害起了加强说明的作用,老米的思维真是……

不过可能要纠正你一个小小的错误哦

貌似逻辑的基本原则是,A->B,否B->否A, 套到题中应该是，A（如果语言中心在左脑）->B( 左脑受损后语言中心一定被破坏), 否B(如果左脑受损后语言中心没有被破坏)->否A(语言中心不在左脑)