again from lsat,thanks

zephyr1977

5题意没看明白,
5.All 250 of the city's Democratic ward leaders were polled about the number of registered Republicans who became registered Democrats during the year. From the reports of the 20 leaders who replied to the questionnaire, we know that altogether they received a total of 500 former Republicans into the Democratic party within the year. Projecting from this sample, we conclude that at least 6,000 Republicans became Democrats　during the year.

　　Which one of the following statements, if true, most clearly undermines the conclusion?

　　(A) Several years ago, 5,000 members of the Republican party registered as Democrats.
　　(B) The more than 90 percent of ward leaders not replying had no former Republicans registering as Democrats.
　　(C) Because they were too busy, more than 90 percent of the ward leaders did not reply percent of the ward leaders did not reply
　　(D) A number of the newly registered Democrats returned to the Republican party at a later date.
　　(E) Similar figures can be produced from past years for registrationchanges from the Democratic party to the Republican party

18. If there is a decrease in the number of homeless families, then either the number of available jobs has increased or else the cost of renting or purchasing housing has decreased. If the cost of renting or purchasing housing has decreased, then the supply of housing must be greater than the demand.
　
　　Assume that there is a decrease in the number of homeless families. 　　According to the passage, which one of the following statements. CANNOT be true?

　　(A) The number of jobs has been decreasing.
　　(B) The cost of renting or purchasing housing has been decreasing, and housing has been decreasing, and housing supply exceeds demand.
　　(C) The number of jobs has been increasing, and the cost of renting or purchasing housing has been stable.
　　(D) The number of jobs has been decreasing, the cost of renting or purchasing housing has been decreasing, and housing demand exceeds supply.
　　(E) The number of jobs has been increasing, the cost of renting or purchasing housing has been increasing, and housing supply exceeds demand.

[em01][em01][em01]请帮忙解释,谢谢

zephyr1977

谢谢详尽耐心的解释,那么笨我也明白了.

licheng

抱歉，第一提没有仔细看，完全凭经验在猜想：）
实际应该是B。

补充一下TONGXUN的理由。

第一提：
很明显，这个题目的ASSUMPTION就是说那些其他的DEMO也是按相同比例地招人。

按照KAPLAN的说话，最强有力的反驳就是把这个ASSUMPTION拨掉，
因此选B是最恰当的。

至于我为什么上来就选D呢？
原因是这样的：
经常有些逻辑题目中的答案不是最长的，反而是最简单的，
而且这些答案是把那些在提干中的矛盾进行调和。
所以我上当了。。。哈哈

但是如果细细地读，一定可以把B选到。

第二题目中，
这样的题目很明显是在推理，
类似于前面JESSICA问的那个 RADAR 什么的，（可以看前面的帖子）
不同的是这里问的是结论，不是假设
但是没关系，一样看。

Ａ＝》Ｂ　ＯＲ　Ｃ
Ｃ＝》Ｄ

现在知道Ａ成立，那么Ｂ或者Ｃ都可以成立。
注意：　Ａ成立，不代表～Ｂ就不行了。
因此，Ａ，Ｂ，Ｃ都是没有问题的。
唯一的问题在Ｄ，Ｅ。
就象ＴＯＮＧＸＵＮ说的，
Ｄ的最后出了问题，而Ｅ是可以成立的，理由如上（注意中）所书。

尤其注意：
Ａ＝》Ｂ，只是说Ａ是Ｂ的　充分条件，没有说～Ａ＝》～Ｂ。
大家应该复习一下初中的冲要条件的讨论。

谢谢

tongxun

D中最后的一段话与原文冲突：housing demand exceeds supply

zephyr1977

B. D
18题似懂非懂,等待高人点拨