费费逻辑91题求教，关于if和only if

Beilo · 发表于 2012-4-17 14:17:57

91. Leachateisasolution, frequently highly contaminated, that develops when water permeates a landifill’s site. Ifand only if the landfill’s capacity to hold liquids is exceeded does the leachate escape into the environment, generally in unpredictable quantities. A method must be found for disposing of leach ate. Most landfill leachateis sent directly to sewage treatment plants, but not all sewage plants are capable of handling the highly contaminated water.

Which one of the following can be inferred from the passage?

A. The ability to predict the volume of escaping landfill leachate would help solve the disposal problem.

B. Ifany water permeates a landfill, leachate will escape into the environment.

C. No sewage treatment plants are capable of handling leachate.

D. Some landfill leachateis sent to sewage treatment plants that are incapable of handling it.

E. If leachate does not escape from a landfill into the environment, then the landfill’s capacity to hold liquids has not been exceeded.

参考答案E

思路：原文说：“Leachate（浸析液）是一种水渗透过垃圾填埋地后生成的溶液，这种溶液通常是高度污染的。
当且仅当超出垃圾填埋的容水能力时（A），Leachate会泄露到外界环境中（B）。必须找到一种处理L的方法。许多L被送去用于污水灌溉，但不是所有的污水灌溉的植物都有能力处理这种被高度污染的水”。

原文中If and only if A then B(从B可推出A)；选项E为If not A then not B（非A推非B）正确

对于此题的解释还是不懂哎……
A：超出处理能力
B：会泄露
原文：ifand only ifA, then B
即为Ｂ→Ａ　
而Ｅ选项是非Ｂ→非Ａ啊…………为什么解释给的是非Ａ→非Ｂ？不是if not B ,then not A 吗？
求教TT

费费逻辑91题求教，关于if和only if

所属分类: GMAT考试

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