费费笔记中的充分必要条件

晴天小狗

谢谢gonghao

晴天小狗

再问：

feifei-91. Leachate is a solution, frequently highly contaminated, that develops when water permeates a landfill’s site. If and 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 leachate. Most landfill leachate is 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) If any water permeates a landfill, leachate will escape into the environment.

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

(D) Some landfill leachate is 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.
        

if and only if 怎么处理？充分且必要？

if and only if 怎么处理？充分且必要？

晕了... E是他的逆否，这又是怎么回事？

晕了... E是他的逆否，这又是怎么回事？

[此贴子已经被作者于2006-10-17 11:30:49编辑过]

晴天小狗

再这个

93. The efficiency of microwave ovens in destroying the harmful bacteria frequently found in common foods is diminished by the presence of salt in the food being cooked. When heated in a microwave oven, the interior of unsalted food reaches temperatures high enough to kill bacteria that cause food poisoning, but the interior of salted food does not. Scientists theorize that salt effectively blocks the microwaves from heating the interior.

Which one of the following conclusions is most supported by the information above?

(A) The kinds of bacteria that cause food poisoning are more likely to be found on the exterior of food than in the interior of food.

(B) The incidence of serious food poisoning would be significantly reduced if microwave ovens were not used by consumers to cook or reheat food.

(C) The addition of salt to food that has been cooked or reheated in a microwave oven can increase the danger of food poisoning.

(D) The danger of food poisoning can be lessened if salt is not used to prepare foods that are to be cooked in a microwave oven.

(E) Salt is the primary cause of food poisoning resulting from food that is heated in microwave ovens.

原文说 有盐不好，D说没盐好。 这两个是逆否？

晴天小狗

再：

107. Because of the recent transformation of the market, Quore, Inc., must increase the next two years, or it will certainly go bankrupt. In fact, however, Quore’s production structure is such that if a 10 percent productivity increase is possible, then a 20 percent increase is attainable.

If the statements above are true, which one of the following must on the basis of them also be true?

1. Because of the recent transformation of the market, Quore, Inc., must increase the next two years

must后为必要？ 也就是 transformation-->Q increase?

2. increase the next two years, or it will certainly go bankrupt

A, or B=  非A-->B？ 即not increase-->bankrupt?

晴天小狗

tmd 烦人

晴天小狗

up

晴天小狗

好

晴天小狗

up

tulip8292

非常感谢，看了一下午FeiFei也没弄明白，现在终于明白了。对于没有任何基础的人，直接就看FeiFei的逻辑讲义好像有点难啊，他的讲义都是结论性的重点，没有解释，我看的一头雾水

kuizee

2位实在厉害！