workhard77

7. If Sarah were a concert pianist for a major orchestra, she would be famous. She is not a concert pianist since she is not famous.

The conclusion above is unsound because the author does not consider that

(A) Sarah could be a famous actress.

(B) Sarah could be a harpist for a major orchestra.

(C) Sarah could be a pianist with a rock group.

(D) Sarah could be a concert pianist with a minor orchestra.

(E) Sarah could be famous for another reason.
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If 1, then 2.=>2是1的必要条件  （这里避免混淆不用一般的A or B or C表示，改用1、2、3 ）
等价于：非2=>非1
这里
1=Sarah were a concert pianist for a major orchestra
2=would be famous
3=be a concert pianist (不等于1)
题干推理过程：
非2=>非3，错误
我认为答案要反对原推理，应指出Sarah still can be a concert pianist （即3可能对）
找"concert pianist"，so D
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workhard77

6. 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.
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首先说明这好像是lsat中专有的题目，gmat中没见过
答案D
看题干：
第一句
=〉senator=not spoke at the convention+spoke at the convention (only if he Democrat)
=〉senator与Democrat的交集spoke at the convention
第二句
=〉“Democrat+senator+spoke at the convention”三者和一的情况为零

SO, No senator spoke at the convention. （画张文氏图更明了）
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[此贴子已经被作者于2002-10-23 0:54:42编辑过]

workhard77

8. Neuroscientists are making progress in discovering more about the cause of Alzheimer's disease. Alzheimer's disease patients suffer from dementia and sever memory loss. Autopsies performed on such patients have revealed the presence of brain lesions caused by abnormal protein deposits. Similar deposits are also found in the brains of elderly patients who do not suffer from Alzheimer's disease. It follows that [U]everyone[/U] who lives long enough will eventually develop Alzheimer's disease.

Which one of the following statements, if true, most seriously undermines the conclusion that everyone who lives long enough will eventually develop Alzheimer’s disease?

(A) The lesions found in the brains of non-Alzheimer's disease patients are far less extensive than those found in the brains of Alzheimer’s disease patients.
(B) The developing brain produces a greater number of cells than it will ever use. The extra cells are later destroyed by what biologists call “programmed cell death.”
(C) The procedure that allows scientists to discover the presence of protein deposits during an autopsy is not yet refined enough to ensure detection of the lesions in all patients.
(D) Autopsies have shown that some people lack the chemical necessary for protein deposits to cause brain lesions.
(E) Though most Alzheimer’s disease patients develop the disease when they are in their late fifties to early seventies, the frequency of patients who develop the disease in their forties is on the rise.
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结论：所有人只要足够老都会得Alzheimer's disease. （我认为关键在everyone）
evidence：验尸说明Alzheimer's disease患者存在由反常蛋白质沉淀物造成的大脑损伤，在非Alzheimer's disease患者的大脑中也存在类似物质。

答案D，切断evidence和结论的关系，说明蛋白质沉淀物需要与chemical necessary共同作用才能造成对大脑的损伤（brain lesions），而some people lack，所以not "everyone"会得Alzheimer's disease

A. 强调了范围"far less extensive"，不能直接削弱
B. 无关
C. 与原论据相悖，在CR中我们必须相信题干所述的真实性
E. "most", "frequency"都只能说明特殊情况

byw:
刚刚这题我也有点迷糊
想来想去只有这么解释了 ，也许有更好的。洗耳恭听：）
ok,该睡觉了的说...
[em19]

[此贴子已经被作者于2002-10-23 0:58:17编辑过]