熱血背包客莊ㄟ

Certain extremely harmful bacteria found only in sewage are difficult to detect directly. Testing for E. coli, an easily detected and less harmful type of bacteria, in ocean water would be a reliable way of determining whether or not these more harmful bac-teria are present, since ocean water contains E. Coli only if the water is contaminated with sewage that contains the harmful bacteria.

Which of the following, if true, most seriously weakens the argument?

(A) There are many different strains of the E. coli bacteria, and only some of these strains are harmful.

(B) Some types of bacteria found in sewage are neither disease-causing nor difficult to detect directly.

(C) Some of the types of bacteria found in sewage along with E. coli are not harmful to people unless the bacteria are ingested in large quantities.

(D) E. coli dies out much more quickly than some of the more harmful bacteria found in sewage and then can no longer be easily detected.

(E) Some of the types of bacteria found in sewage along with E. coli reproduce at a slower rate than E. coli.

logic book style

Premise1：Certain extremely harmful bacteria found only in sewage are difficult to detect directly.

Premise2：E. coli, an easily detected and less harmful type of bacteria

Premise3：since ocean water contains E. Coli only if the water is contaminated with sewage that contains the harmful bacteria.

Conclusion：Testing for E. coli in ocean water would be a reliable way of determining whether or not these more harmful bacteria are present,

中文對照：

前提一：爛泥中的致命細菌難找

前提二：ＥＣ好找，不致命（這個是結論據當中的同位語描述，他用來當說明用的，這意味著是一個前提屬性用來限定為何我要找EC）

前提三：水被污染情況下，有ＥＣ，必有致命細菌

結論：ＥＣ對致命細菌觀測很可靠

再來就是把一些混淆視聽的東西去除，就是把irrelevancies，inconsisten，cross-references給找出來並調整，不過這裡不太需要去蕪存菁了，感覺上都滿精簡

分類完之後就是找連貫性（coherence），ＥＣ對致命細菌之間的消長，然後題目問weaken這個削弱的意思就是想辦法將整個argument變成爛的argument，所以可以有以下質疑處，可以詢問前提是否為真，結論是否有反例出現，基本上這兩招吃遍所有加強跟削弱題。

選項：

(A) There are many different strains of the E. coli bacteria, and only some of these strains are harmful.

直接探討到ＥＣ的屬性毒性特徵，這跟文章連貫性不符，也跟前提二內容有出入，不用去討論加強或削弱了，直接刪

(B) Some types of bacteria found in sewage are neither disease-causing nor difficult to detect directly.

跟選項（Ａ）同樣症狀病徵

(C) Some of the types of bacteria found in sewage along with E. coli are not harmful to people unless the bacteria are ingested in large quantities.

明明就在討論檢測方式，這裡還在題各菌種屬性

(D) E. coli dies out much more quickly than some of the more harmful bacteria found in sewage and then can no longer be easily detected.

這個前提二相反，所以可以證明前提二對是對，但是活不久的話就不能去連結有ＥＣ就共存致命細菌， E. coli dies，死得快就不會傷害到別人了，然後死了就找不到了 對比ＥＣ好找

補充：這種歸納類的題型就是只要從一開始的前提一直到結論，中間沒有任何差錯，從上推到下，從一推到結論，中間是一直連接的，這樣才有可能是可有效且好的論辯，假設中間任何一句話被推翻，這個歸納就存在，這樣就達到weaken的效果，在簡單一點就是，爛泥中的致命細菌難找→ＥＣ好找，不致命→水被污染情況下，有ＥＣ，必有致命細菌→ＥＣ對致命細菌觀測很可靠，當中只要一個箭頭對不過去下一個關卡，這就是weaken

這類似數學歸納法的處理方式，

當n=1時，3n+1 = 4，不是3的倍數，這時候你可以想成前提一

當n=2時，3n+1= 7，也不是3的倍數，這時候你可以想成前提二

我假設 n=k 也不是3的倍數是成立的，這時可假設前提三

那麼我 n= k+1的情況之下，不是3的倍數必定也會成立，這個就是結論

所以以上如果有個n算出來是3的倍數，這組數學歸類都會無法得証

(E) Some of the types of bacteria found in sewage along with E. coli reproduce at a slower rate than E. coli.

看到繁殖速度就可以大膽刪除

選（Ｄ）

我認為GRE的錯誤選項是定義上的問題，角色扮演上的錯誤，而不是翻譯內容上的瑕疵讓他產生錯誤，所以要從定義著手才是王道，以上個人筆記希望有幫助到大家，文章內容中英夾雜請見諒，有誤再請指教!!