请教LSAT19II-11,12

superkun

11. A controversial program rewards prison inmates who behave particularly well in prison by giving them the chance to receive free cosmetic plastic surgery performed by medical students. The program is obviously morally questionable, both in its assumptions about what inmates might want and in its use of the prison population to train future surgeons. Putting these moral issues aside however the surgery clearly has a powerful rehabilitative effect as is shown by the fact that, among recipients of the surgery the proportion who are convicted of new crimes committed after release is only half that for the prison population as a whole.
A flaw in the reasoning of the passage is that it
(A) allows moral issues to be a consideration in presenting evidence about matters of fact
(B) dismisses moral considerations on the grounds that only matters of fact are relevant
(C) labels the program as "controversial" instead of discussing the issues that give rise to controversy
(D) asserts that the rehabilitation of criminals is not a moral issue
(E) relles on evidence drawn from a sample that there is reason to believe is unrepresentative
answer: E why?


12. The retina scanner a machine that scans the web of tiny blood vessels in the retina, stores information about the pattern formed by the blood vessels. This information allows it to recognize any pattern it has previously scanned. No two eyes have identical patterns of blood vessels in the retina. A retina scanner can therefore be used successfully to determine for any person whether it has ever scanned a retina of that person before.
The reasoning in the argument depends upon assuming that
(A) diseases of the human eye do not alter the pattern of blood vessels in the retina in ways that would make the pattern unrecognizable to the retina scanner
(B) no person has a different pattern of blood vessels in the retina of the left eye than in the retina of the right eye
(C) there are enough retina scanners to store information about every person's retinas
(D) the number of blood vessels in the human retina is invariant although the patterns they form differ from person to person
(E) there is no person whose retinas have been scanned by two or more different retina scanners
answer: A  我觉得B好象也对？

谢谢各路英雄！

mjiirggh

1. 可以用排除法去掉ABCD. A和B错在原文在做结论时并没有考虑moral issue, 或是说moral issue不是结论的premises. C错. 原文正是讨论issue. D错,原文没有出现. E指出了原文论证的问题.
原文讲给表现好的犯人机会做美容手术. 根据这些人被释放后又犯罪的比例是所有犯人总体的比例的一般说明此program有效. 这里的假设是美容手术起到了作用. 但是原文忽略的是做美容手术的犯人本身就是表现好的犯人, 他们本来再犯罪的比率就小(common sense), 所以通过对这个sample的观察得到关于美容手术的结论有问题.
2. 你关于左右眼自己做了什么assumption? 是scanner有时查左眼有时查右眼? 根据题目我们得不到关于左右眼的结论, B是out of scope.

superkun

many thanks !!