新手请教：”取非“是什么意思？多谢！

snowflower

经常看到RC 和CR里有讲“取非”laba, laba,请问取非是什么意思啊？是把问题取非还是把原文取非，还是答案取非？是把一句话的前半部分取非还是后半部份取非？为什么要取非？晕了！

dansy

取非是逻辑题里区分支持和前提的一种技巧。对于前提的题目，一般你读完题干后，对五个选项进行分析，可能排除三个，最后剩的两个一个是正确选项，一个是干扰项，这时你对这两个选项分别取非。取非是指对句子谓语动词取非，比如原文说“是”，取非就是“不是”，原文是do, 取非就是dont。碰到复合句，是对主句取非。取非后看这两个选项的区别，如果取非后原文结论瓦解，则这个选项为前提。如果取非后，原文结论不能瓦解，比如说只是削弱原文结论，则这是干扰项。


如果还有疑问，可附上一例题来解释。

snowflower

dansy, thank you!


e.g.


In the years since the city of London imposed strict air-pollution regulations on local incustry, the number of bird species seen in and around London has increased dramatically.     Similar air-pollution rules should be imposed in other mahor cities.


Each of the following is an assumption made in the argument above EXCEPT:


(A) In most mahor cities, air-pollution problems are caused almost entirely by local industry.


(B) Air-pollution regulations on industry have a significant impact on the quality of the air.


(C) The air-pollution problems of other cities are basically similar to those once suffered by London.


(D) An increase in the number of bird species in and around a city is desirable.


(E) The increased sightings of bird species in and around London reflect an actual increase in the number of species in the area.


should    this question use the "Negate Option"?     the correct answer is A.     BUT WHY???


THANKS AGAIN!

zcx

请问dansy, 你这么清楚地逻辑方法是在什么地方学的呀？

dansy

以下是引用snowflower在2004-3-21 6:57:00的发言：
dansy, thank you!



e.g.


In the years since the city of London imposed strict air-pollution regulations on local incustry, the number of bird species seen in and around London has increased dramatically.     Similar air-pollution rules should be imposed in other mahor cities.


Each of the following is an assumption made in the argument above EXCEPT:


(A) In most mahor cities, air-pollution problems are caused almost entirely by local industry.


(B) Air-pollution regulations on industry have a significant impact on the quality of the air.


(C) The air-pollution problems of other cities are basically similar to those once suffered by London.


(D) An increase in the number of bird species in and around a city is desirable.


(E) The increased sightings of bird species in and around London reflect an actual increase in the number of species in the area.


should    this question use the "Negate Option"?     the correct answer is A.     BUT WHY???


THANKS AGAIN!

snowflower MM，这题严格说来不是我上贴应用方法来区分支持和前提的典型例子。这样的例子在以前的帖子里可以找到，你用搜索试试。因为我现在手头没有GMAT资料，所以不能提供一个例子。见谅。


这题是在用前提建立city of London 和other major cities 之间的某种对等关系。A的错误可以在和B的比较中看出来。你可以象B说的工业污染有很大影响，但是不能说污染几乎全来自工业污染。关于city of London的描述中没有这个意思。

coolcubbit

取非是逻辑题里区分支持和前提的一种技巧。对于前提的题目，一般你读完题干后，对五个选项进行分析，可能排除三个，最后剩的两个一个是正确选项，一个是干扰项，这时你对这两个选项分别取非。取非是指对句子谓语动词取非，比如原文说“是”，取非就是“不是”，原文是do, 取非就是dont。碰到复合句，是对主句取非。取非后看这两个选项的区别，如果取非后原文结论瓦解，则这个选项为前提。如果取非后，原文结论不能瓦解，比如说只是削弱原文结论，则这是干扰项。


如果还有疑问，可附上一例题来解释。

-- by 会员 dansy (2004/3/18 10:20:00)

啊  dansy简直是我的救星啊