a last question to discuss

spry

this is for one of my net friends.

No senator spoke at the convention unless he or she was a
Democrat. No Democrat both spoke at the convention and was a senator

Which one of the following conclusions can be correctly drawn from
the statements above?

(A) N one but senators spoke at the convention.

(B) No Democrat spoke at the convention.

(C) Only Democrats spoke at the convention.

(D) No senator spoke at the convention.

(E) Some Democrat senators spoke at the convention.

Do you have any idea how to kill this kind of questions??

tongxun

答案：D。我是死做出来的---世界上最笨的方法！
1、可能性：只有民主党议员讲话
2、现实性：讲话的民主党人，没有议员。
推出：没有民主党议员讲话。
象这种在提干中，全是绝对性语言的题目，找绝对性选项；题目的重点在“民主党议员”，找有它的选项。

spry

我画了个文氏图.我也觉得D对。。可是不知道给的答案是哪个。

tongxun

经过再三比较，我认为肯定是D。一开始还想用集合说明，但后来又觉得不对。

crackok

高手,我清楚记得是答案D.
有意思的是我第一次做也用文氏图.第二次,就按TX的方法.可见异曲同工.
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我们的口号是：路虽远，行则必至；事虽难，做则必成。

workhard77

我觉得文氏图挺麻烦，一时也想不出怎么画，我到愿意直接从字面理解逐一排除。

pgclt

What's 文氏图?

My approach:
I) No senator spoke at the convention unless he or she was a
Democrat. => If a senator spoke at the convention, then he or she was a Democrat.

II) No Democrat both spoke at the convention and was a senator.

from I, senator+spoke-> democrat.
from II, democrat -> NO(senator+spoke)

I and II denies each other. If both I and II are true, then no senator can speak.

tongxun

spry： What's 文氏图?

spry

it is Venn diagram which can be used to show the relationship between sets.
rings a bell? remember we use a circle to show a set..........

crackok

就是集合中的圈圈嘛.
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我们的口号是：路虽远，行则必至；事虽难，做则必成。