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请教沸沸逻辑63题的一个选项

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楼主
发表于 2008-11-7 15:14:00 | 只看该作者

请教沸沸逻辑63题的一个选项

63. Some good cooks are gourmet cooks who pride themselves on always using extravagantly rich ingredients in elaborate recipes. Some good cooks can be characterized as fast-food cooks. 
They may use rich ingredients as long as the recipes are easy to follow and take little time. Other good cooks are health food enthusiasts, who are concerned primarily with the nutritional value of food. 
But even though not all good cooks are big eaters, they all enjoy preparing and serving food. 
If the information in the passage is true, which one of the following CANNOT be true? 
(A) Most good cooks do not use extravagantly rich ingredients. 
(B) Everyone who enjoys preparing and serving food is a good cook. 
(C) More good cooks who use extravagantly rich ingredients are big eaters than are good cooks who do not use such ingredients. 
(D) There are fewer good cooks who enjoy serving and preparing food than there are good cooks who are big eaters. 
(E) Gourmet cooks, fast-food cooks, and cooks who are health food enthusiasts are all big eaters.
答案D没问题,问题是B,沸沸里的解释是“从结论可以推出”,但是我觉得不对啊。题干说good cooks都喜欢准备……,但是B明显说反了啊。这个不就是类似A
推出B,说明B也能推出A的错误吗?请高人指教,谢谢!

[此贴子已经被作者于2008-11-7 15:18:17编辑过]
沙发
发表于 2008-11-7 15:36:00 | 只看该作者
同问
板凳
发表于 2008-11-7 16:00:00 | 只看该作者

1楼贴出来的题目,不完整。这个是完整版本的:

63. Some good cooks are gourmet cooks who pride themselves on always using extravagantly rich ingredients in elaborate recipes. Some good cooks can be characterized as fast-food cooks. They may use rich ingredients as long as the recipes are easy to follow and take little time. Other good cooks are health food enthusiasts, who are concerned primarily with the nutritional value of food. But even though not all good cooks are big eaters, they all enjoy preparing and serving food.
If the information in the passage is true, which one of the following CANNOT be true?

(A) Most good cooks do not use extravagantly rich ingredients.
(B) Everyone who enjoys preparing and serving food is a good cook.
(C) More good cooks who use extravagantly rich ingredients are big eaters than are good cooks who do not use such ingredients.
(D) There are fewer good cooks who enjoy serving and preparing food than there are good cooks who are big eaters.
(E) Gourmet cooks, fast-food cooks, and cooks who are health food enthusiasts are all big eaters.

不过,我也觉得这道题目很蹊跷。放过算了。考试若真遇到,算自己倒霉好了。

地板
发表于 2008-11-7 22:21:00 | 只看该作者
我刚开始也愣了一下,仔细看,题目是CANNOT BE TRUE
也就是说充分条件,必要条件,都可能是true。比如E,Gourmet cooks, fast-food cooks, and cooks who are health food enthusiasts是必要条件,有可能是他们good cooks, 进而由必要条件得出他们有可能是big eaters,但并不是充分条件。同理,B也是必要非充分。

充分非必要也是may be true的选项。也就是说,原命题,逆命题都有可能true(虽然可能非充分,或非必要)但是D不同,既充分也非必要,完全没有可能推出来的结论,才是CANNOT BE TRUE

所以对这类题A -> B, CANNOT BE TRUE的选项就是“A不能推出B”或者“A推出B的补集”

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