og12-71

akness

这道题我怎么看都不明白，请赐教！
71. Roland: The alarming fact is that 90 percent of the people in this country now report that they know someone
who is unemployed.
Sharon: But a normal, moderate level of unemployment is 5 percent, with one out of 20 workers unemployed.
So at any given time if a person knows approximately 50 workers, one or more will very likely be unemployed.
Sharon’s argument relies on the assumption that
(A) normal levels of unemployment are rarely exceeded
(B) unemployment is not normally concentrated in geographically isolated segments of the population
(C) the number of people who each know someone who is unemployed is always higher than 90 percent of
the population
(D) Roland is not consciously distorting the statistics he presents
(E) knowledge that a personal acquaintance is unemployed
答案是B

taner

是不是这个意思，如果失业人口密集在某一地区，那么一个认识五十个人的人认识的这五十个人中就不一定会出现失业的人。那么S的说法就不会成立。

sunyan730

是不是这个意思，如果失业人口密集在某一地区，那么一个认识五十个人的人认识的这五十个人中就不一定会出现失业的人。那么S的说法就不会成立。
-- by 会员 taner (2009/11/18 9:47:29)

嗯，是的。这是一个排除削弱的答案。你把这个答案取非，看看能不能削弱s的结论。如果能的话这个答案就是正确的。
取非：
unemployment is normally concentrated in geographically isolated segments of the population。失业一般集中在人口处于地域上相对隔离的地方。（不知道我翻译的是否正确?）如果是这样的话，那么s的结论就不具代表性，而s说的是But a normal, moderate level of unemployment is 5 percent, with one out of 20 workers unemployed.，正常的失业率是5%。也就是说驳斥了normal。
小小拙见，望nn批评指正。