GRE閱讀｜What causes a helix in nature to appear with either a dextral (right-handed, or clockwise) twist or a sinistral (left-handed, or counterclockwise) twist－熱血背包客莊ㄟ

What causes a helix in nature to appear with either a dextral (right-handed, or clockwise) twist or a sinistral (left-handed, or counterclockwise) twist is one of the most intriguing puzzles in the science of form. Most spiral-shaped snail species are predominantly dextral. But at one time, handedness (twist direction of the shell) was equally distributed within some snail species that have become predominantly dextral or, in a few species, predominantly sinistral. What mechanisms control handedness and keep left-handedness rare?

It would seem unlikely that evolution should discriminate against sinistral snails if sinistral and dextral snails are exact mirror images, for any disadvantage that a sinistral twist in itself could confer on its possessor is almost inconceivable. But left- and right-handed snails are not actually true mirror images of one another. Their shapes are noticeably different. Sinistral rarity might, then, be a consequence of possible disadvantages conferred by these other concomitant structural features. In addition, perhaps left- and right-handed snails cannot mate with each other, having incompatible twist directions. Presumably an individual of the rarer form would have relative difficulty in finding a mate of the same hand, thus keeping the rare form rare or creating geographically separated right- and left-handed populations.

But this evolutionary mechanism combining dissymmetry, anatomy, and chance does not provide an adequate explanation of why right-handedness should have become predominant. It does not explain, for example, why the infrequent unions between snails of opposing hands produce fewer offspring of the rarer than the commoner form in species where each parent contributes equally to handedness. Nor does it explain why, in a species where one parent determines handedness, a brood is not exclusively right- or left-handed when the offspring would have the same genetic predisposition. In the European pond snail Lymnaea peregra, a predominantly dextral species whose handedness is maternally determined, a brood might be expected to be exclusively right- or left-handed—and this often occurs. However, some broods possess a few snails of the opposing hand, and in predominantly sinistral broods, the incidence of dextrality is surprisingly high.

Here, the evolutionary theory must defer to a theory based on an explicit developmental mechanism that can favor either right- or left-handedness. In the case of Lymnaea peregra, studies indicate that a dextral gene is expressed during egg formation; i.e., before egg fertilization, the gene produces a protein, found in the cytoplasm of the egg, that controls the pattern of cell division and thus handedness. In experiments, an injection of cytoplasm from dextral eggs changes the pattern of sinistral eggs, but an injection from sinistral eggs does not influence dextral eggs. One explanation for the differing effects is that all Lymnaea peregra eggs begin left-handed but most switch to being right-handed. Thus the path to a solution to the puzzle of handedness in all snails appears to be as twisted as the helix itself.

1.Which of the following would serve as an example of “concomitant structural features” that might disadvantage a snail of the rarer form?

(A) shell and body that are an exact mirror image of a snail of the commoner form

(B) A smaller population of the snails of the rarer form

(D) A pattern on the shell that better camouflages it

(E) A smaller shell opening that restricts mobility and ingestion relative to that of a snail of the commoner form

2.The second paragraph of the passage is primarily concerned with offering possible reasons why

(A) it is unlikely that evolutionary mechanisms could discriminate against sinistral snails

(B) sinistrality is relatively uncommon among snail species

(D) a theory based on a developmental mechanism inadequately accounts for the predominance of dextrality across snail species

(E) dextral snails breed more readily than sinistral snails, even within predominantly sinistral populations

3.Which of the following accurately describes the relationship between the evolutionary and developmental theories discussed in the passage?

(A) Although the two theories reach the same conclusion, each is based on different assumptions.

(B) They present contradictory explanations of the same phenomenon.

(D) The second theory demonstrates why the first is valid only for very unusual, special cases.

(E) They are identical and interchangeable in that the second theory merely restates the first in less technical terms.

4.It can be inferred from the passage that a predominantly sinistral snail species might stay predominantly sinistral for each of the following reasons EXCEPT for

(A) a developmental mechanism that affects the cell-division pattern of snails

(B) structural features that advantage dextral snails of the species

(D) anatomical incompatibility that prevents mating between snails of opposing hands within the species

(E) geographic separation of sinistral and dextral populations

5. In describing the "evolutionary mechanism" (the first sentence of the third paragraph), the author mentions which of the following?

(A) The favorable conditions for nurturing new offspring

(B) The variable environmental conditions that affect survival of adult snails

(D) The structural identity of offspring to parents of the same hand

(E) The frequency of unions between snails of different species

6. According to the passage, which of the following is true of Lymnaea peregra?

(A) Handedness within the species was at one time equally distributed between left and right.

(B) Under laboratory conditions, dextral eggs from Lymnaea peregra can be artificially induced to develop into sinistral snails.

(D) Handedness in Lymnaea peregra offspring is determined by two parents together.

(E) fewer sinistral offspring in dextral broods than dextral offspring in sinistral broods

結構分析：

以段為單位來呈現好了，之前去補習班一聽到老師在那邊翻譯翻的狗屁不通，就像是把google翻譯上面的東西拿出來照念而已，然後唸完之後就說所以這題選Ａ，接著就開始講一些跟課堂無關的幹話。他媽的那我幹媽浪費錢花時間去補習班啊，我叫Siri唸給我聽就好了啊，因而我憤而自己讀。

第一段：

第一句抓個重點發現他媽的再丟問題給我啊，他說什麼東西導致左旋跟右旋，然後本來期待他給我答案的，結果他給我一個字puzzles差點想打作者，這個答案比取決於旋渦鳴人轉動螺旋丸的方向而定還要更無言，所以這個主題句感覺沒麼啥意義，唯一能知道的方向可能就是要來解答造成左旋跟右旋的原因是什麼，資訊大概就這麼多了，往下看吧

Most spiral-shaped snail species are predominantly dextral.

第二句開頭給個most這個字出現就表示作者在下條件了，他的用意就是在說在大部分的情況下，我後面說的事情都是對的，所以代表有例外之情形，因此他是在做條件上的舉例的，不值得一看，跳過。

But at one time, handedness (twist direction of the shell) was equally distributed within some snail species that have become predominantly dextral or, in a few species, predominantly sinistral.

來到第三句，這更扯淡，雖然有一個BUT拉，這個是作為上一句話的Most做對比，但是呢at one time，管你翻作曾經還是有一次，這不都是舉例的訊號字嗎？

理由一：

at one time表示歷史上的某個時間點，他突然發生一件事情被紀錄下來，某個時間點為連續時間當中的節點，y=f(X)的Ｘ，而某節點所代表的事情並不能代表整個歷史，無法光看一個點把方程式給求出來或畫出來，所以屬於舉例用。

理由二：

這個『曾經』就是那個談話性綜藝節目最愛用的單字啊，當主持人問到某個藝人的時候，那個藝人就會說先根據主持人在寫生板的厚紙板上被裝飾的很漂亮的圖卡上的彩色貼膜撕下來可以看到的具有少女風格或是文青風格字體的題目來下評估他覺得那個題目帶給被問問題的那個藝人本身感覺是好還是壞，他們通常都會給你一個表達他覺得心情好壞的形容詞評語，之後開始講：『曾經有一次我朋友怎樣怎樣.....』去服務為何要說前面的形容詞，啊對～有時候我都覺得他們在舉例很奇怪，明明題目問自身的感受，卻舉個朋友的感想出來，這種文不對題的回答方式還滿妙的主詞不同不能對等，除非你要加上一個並列邏輯在內，阿不然就是拿自身週遭經驗去以偏概全，例如：自己覺得某個地方很好玩，所以大家都要覺得自己說的那地方也是很好玩，或是自己遇到某個國家來的當地人很爛，因此推敲出這個國家的人都跟他所說的那個當地人一樣爛，我認為這都是一個論文當中絕對不允許被使用的低級錯誤，但既然是綜藝節目看看笑笑就好，我沒有任何暗示，我只是提醒自己寫作考試不要這樣寫，跟教授面試不要這樣講而已。

撲這麼多梗就是要說服眾生這個at one time就是舉例的訊號字拉～，既然是舉例就是細節用來支持概念或主旨用的，那我們一開始看到文章就是先抓主旨在說，細節有考在看，阿最近中秋節要到了，一樣啊，基本的烤肉用具先買啊，然後烤肉就是主幹，所以肉一定也要先買回來醃，然後像是飲料這種東西就是細節了啊～不夠再買，或者是要喝再買，也不用浪費冰箱的容積（不浪費大腦記憶）。

What mechanisms control handedness and keep left-handedness rare ?

最後，疑問句又放句尾，請對他喊I got you!! I got you!! I got you!!，他也很爭氣得給了兩個重點，因為有and並列結構，所以要分兩組，問題是『怎麼分左右』，然後『左邊又特別少』，這段只需看兩句。

第二段：

It would seem unlikely that evolution should discriminate against sinistral snails if sinistral and dextral snails are exact mirror images, for any disadvantage that a sinistral twist in itself could confer on its possessor（老哥別陷進去啊，關係代名詞修飾劣勢，請跳過） is almost inconceivable.

這裡在刪減之後可以得到主題是演化ＥＶＯ不會變左旋，『 EVO , X sin 』，然後that子句外面給一個否定詞彙unlikely，這表示演化不會往左旋的趨勢走，是假的！！而演化不是原因的條件是左右琁的圖案完全鏡射，他在第二段開頭這樣寫有兩個理由，第一：剛剛第一段拋出的問題是到底是什麼東西引響左右旋，這裡給了否定答案，反正跟演化無關拉～～但有附註條件。第二：會這樣寫的原因當然激起讀者問『為什麼』，所以想必接下來必然一堆舉例來解釋，所以在這個暗示之後我是爽翻天了，因為得到一個答案確定跟演化無關，並且第二段都在舉例，不用看～～～，最後我最關心的就是從哪裡開始不用看。差點忘了講那個for，這個for他不是介系詞喔，他變成連接詞了，當作因為because用，所以才會有一個完整句的結構出現，好的下一句～～～

But left- and right-handed snails are not actually true mirror images of one another.

雖說往下的內容可能都不需要看，可是語氣的轉折，使得這句話要注意，其邏輯要跟上一句話相反，那他們相反在哪呢？？他卻是對剛剛上一句裡面的條件作出轉折，對應到are not 『actually』 true mirror images，這也使得文章邏輯改變了，上一句話說到『 EVO , X sin 』是在鏡射的條件下成立，於是這句話給予的暗示便會形成就是因為左右璇沒有鏡射，因此！！『 EVO , sin 』左旋跟演化是『有』關的，文章在此對演化又繞回來有所贊成之意。

Their shapes are noticeably different.

這個是概念說明，算是上一句話的總結，應為代名詞Their把左旋跟右旋的關係給綁在一起，這句話開頭是代名詞其實不看也無所謂。充其量只是not actually true mirror 同意替換罷了邏輯上延續著對EVO抱持正面態度，不過為了讓考試時間更加充裕，一樣是依照我們的老規局，代名詞，修飾詞亂我主幹者，必殺之！！

Sinistral rarity might, then, be a consequence of possible disadvantages conferred by these other concomitant structural features.

In addition, perhaps left- and right-handed snails cannot mate with each other, having incompatible twist directions.

Presumably an individual of the rarer form would have relative difficulty in finding a mate of the same hand, thus keeping the rare form rare or creating geographically separated right- and left-handed populations.

這三組一起看，作者意圖極度明顯，剛開始我是沒發現他們之間是一個分成三句話的並列結構，直到我看到了In addition, 這個字表示進一步的遞進關係，意味著它跟上一句話必然相關，接著我在看到他們三句之間都有個共同點就是假設語氣的副詞，所以他間接露餡了，接著由它們三組綁在一起成為套件我們再來探討他們的角色扮演是啥，到底是論據還是論點之類的，然而我看到了第一句的a consequence of這表示結論的名詞代表的是前因後果的關係，consequence 後方的內容是在做出原因說明，屬細節部分，對我們的前面做出支持，既然如此我們就要把目光轉向上一句話的那個Sinistral rarity .這組套件應該就是對這個形狀非常『少』的舉例，並且邏輯上還是在維持第一段的問題二：keep left-handedness rare ，對於這樣的角色扮演上是舉例解釋用的，我只要知道Sinistral rarity 就好，延續更上面一句的左右旋不是鏡射的關係，導致EVO確實起到作用。

我來總結一下，考試的時候我只會看第前兩句話（主題句＋轉折句），其他當作不存在，所以唯一直得記得只有『EVO → 左旋』還有Sinistral rarity繼續延續剛剛開頭第一段的問題二。

第三段：

But this evolutionary mechanism combining dissymmetry, anatomy, and chance（關係代名詞無視，不過在文法上這句話太妙了，等等岔開來討論，結構上太美了直得欣賞） does not provide an adequate explanation of why right-handedness should have become predominant.

又來個轉折，注意代名詞this evolutionary mechanism，這到底是誰，因為要連接整個文章的邏輯，前方有轉折，然後後方給了無法證明的負面情緒，連接上去上一段的結果是seem unlikely that evolution should discriminate against sinistral snails這兩句話的邏輯上應該是同向的啊，不應該BUT存在，所以就要來檢視一下這個evolutionary mechanism到底是誰，我發現ETS出題出的是在太美了，我們看到進化機制後方的關代，combining dissymmetry, anatomy, and chance提出了三種概念，第一：不對稱，第二：解剖構造，第三：機運，這三個很剛好的跟剛剛那組細節套件相對應，these other concomitant structural features當中的代名詞就是not actually true mirror images的同意替換＝dissymmetry。再來，incompatible twist directions提出了結構上的不相容。最後，difficulty in finding a mate這不就是類似機運的轉化了嗎？找到對象的機會很難，哈哈跟我這個死宅男一樣存在相同的症狀，真是完美的封裝，所以這前方的代名詞this evolutionary mechanism才會用成單數的就是把它套件化，所以他只是對於剛剛提出的那三種可能性作出反駁，不過你看第三段的開頭既然是反駁上一段話的『細節』內容，這轉折雖沒貴賤之分但有對等地位之別的，這段最重要的一句話是反駁上一段細節，所以第三段在階級分層上，也難登大雅之堂，大雅在台中，是個著名的塞車地點，所以這段我的預測是我認為以下的內容應該是可以忽略掉了，為了證明這間事情我們來喵喵看其他第三段的內容吧。那邏輯『EVO → 左旋』已經被反駁，改回『 EVO , X sin 』

It does not explain, for example, why the infrequent unions between snails of opposing hands produce fewer offspring of the rarer than the commoner form in species where each parent contributes equally to handedness.

看到訊號字for example，很棒忽略一句了，掰掰～～～

Nor does it explain why, in a species where one parent determines handedness, a brood is not exclusively right- or left-handed when the offspring would have the same genetic predisposition.

先說nor這個也是對等連接詞，就是『負and』就對了拉，這麼一來就是不用看的意思了，這個對等連接詞有對到for example喔，所以是作者覺得舉一個例子不夠爽，他老兄老姐再補一刀給你

In the European pond snail Lymnaea peregra, a predominantly dextral species whose handedness is maternally determined, a brood might be expected to be exclusively right- or left-handed—and this often occurs.

本文章只有探討到左旋跟右旋，可是這裡出現了專有名詞，某品種的蝸牛，我管他是哪一種，都在舉例了，還舉出某實際的物種，這已經細節到不行了，我不管他分左選還是右旋，不用看。

However, some broods possess a few snails of the opposing hand, and in predominantly sinistral broods, the incidence of dextrality is surprisingly high.

出線However照慣例必看而且還出現在句尾，他很有可能轉折文章邏輯，好像有點難懂，先把這句話微分再討論吧，有些蛋有一些『反手』蝸牛，這個不太懂他想幹媽，不過後面有and對等連接詞，邏輯上是一樣的，and in predominantly sinistral broods, the incidence of dextrality is surprisingly high.喔喔瞭解了，他意思就是說，左琁蛋生出右旋的鍋牛，好拉就是種瓜『不』得瓜，種豆『不』得豆拉，虎父有犬子，注意到結尾dextrality is surprisingly high.這是繼續呼應左旋很少，這文章實在太了不起了，結尾到會把大家帶回到原本要討論的東西，非常工整。不過話說回來他還是在打轉，沒繼續講重點只是不斷的提醒我們Sinistral rarity 感覺就像是移動迷宮一直在講WICKED is good一樣，或是冰與火之歌the winter is coming.，所以也不用去記筆記了，第三段整個可以忽略定了，就算你有轉折詞吊尾也是一樣。

補充：

剛剛some broods possess a few snails of the opposing hand這句話可以透過並列邏輯去猜出大概的意思，如果這句話要知道的話必須往前找，因為the opposing hand這裡有個定冠詞，表示前面有提過，那往上找大概可以知道他想講得是LP這個蝸牛他決大部分是右旋的但是也有一些是『反向的例外』那就是左旋。

第四段：

Here, the evolutionary theory must defer to a theory based on an explicit developmental mechanism that can favor either right- or left-handedness.

總算是最後一段了，坦白說還真有點累，defer to 基於聽從的意思，間單說當成follow就好了，在更簡單的說就是有後面的東西才會有evolutionary，explicit developmental mechanism 後面關係代名詞，之所以沒被我忽略是因為他在對文章主題做說明，提到EDM是可以決定左跟右的，所以聽命行事表示ＥＶＯ沒有主導權，他沒地位，大哥是對的，EVO都不對，所以一樣是延續文章邏輯『EVO跟左右旋無關』，只是這段給出一個答案就是EDM是可以決定左跟右，因此本文主旨有反駁ＥＶＯ的可行性，並且提出新觀點之意，所以等等如果有出現本文主要是幹麻用的，那個新觀點建立可能是個答案。

In the case of Lymnaea peregra, studies indicate that a dextral gene is expressed during egg formation; i.e., before egg fertilization, the gene produces a protein, found in the cytoplasm of the egg, that controls the pattern of cell division and thus handedness.

一個案例怎樣怎樣的...舉例拉～～非主幹架構也，謝謝再聯絡，而且有Lymnaea peregra這是剛剛忽略過的例子，所以他在文章的架構層次來說還是在細節上打轉。

In experiments, an injection of cytoplasm from dextral eggs changes the pattern of sinistral eggs, but an injection from sinistral eggs does not influence dextral eggs.

實驗也照樣是舉例，我跳

One explanation for the differing effects is that all Lymnaea peregra eggs begin left-handed but most switch to being right-handed.

一樣跳，考試得事後把自己當成那種不問原因只問結果的老闆，所以看到explanation跳

Thus the path to a solution to the puzzle of handedness in all snails appears to be as twisted as the helix itself.

給結論了，幹！！討論完沒給答案，靠腰勒，這作者的文章手法讓我佩服，可他內容還真灑狗血的，不過話說他也完成迴文了這句話跟文章開頭第一句話一樣。然而唯一靠譜的就是developmental mechanism左手寫他～～右手寫這愛，一邊是友情　一邊是愛情，來賓掌聲歡迎gentleman sausage hit accurately 鄭中基，他可決定左跟右

看完之後可能已經頭昏眼花了，所以咱們再來複習一下：

What causes a helix in nature to appear with either a dextral twist or a sinistral twist is one of the most intriguing puzzles in the science of form. What mechanisms control handedness and keep left-handedness rare?

P1: what is the mechchanism influencing a dextral twist and a sinistral twist (relatively rare) ??

P2: Sinistral rarity is caused by evolution that discriminate against sinistral snails

But this evolutionary mechanism combining dissymmetry, anatomy, and chance does not provide an adequate explanation of why right-handedness should have become predominant. However, some broods possess a few snails of the opposing hand, and in predominantly sinistral broods, the incidence of dextrality is surprisingly high.

P3: Evolution dose not make sense, and sinistral snails are rare. The reason for keeping the last sentence in the paragraph 3 is that this is the sentence followed by " however "

Here, the evolutionary theory must defer to a theory based on an explicit developmental mechanism that can favor either right- or left-handedness. Thus the path to a solution to the puzzle of handedness in all snails appears to be as twisted as the helix itself.

P4: Explicit developmental mechanism deciding either right or left handedness is followed by the evolutionary theory. We still ain't got no reasons for the sinistral rarity.

1.Which of the following would serve as an example of “concomitant structural features” that might disadvantage a snail of the rarer form?

(A) shell and body that are an exact mirror image of a snail of the commoner form

(B) A smaller population of the snails of the rarer form

(D) A pattern on the shell that better camouflages it

(E) A smaller shell opening that restricts mobility and ingestion relative to that of a snail of the commoner form

解題：

下列哪一個選項是作為舉例用的，這舉例是在不利於稀有品種蝸牛所相對應的結構特徵，由關鍵字回推文章的那組套件的第一式：

Sinistral rarity might, then, be a consequence of possible disadvantages conferred by these other concomitant structural features

然後看完這句話注意的題目是an example舉例，所以找到的對應點是概念，接下來任務就是要找例子出來，而例子的呈現是去呼應概念，所以要來關注到所謂的structural，他表示結構外型構造，為了要呼應概念，主詞的那個結構特徵就必須是舉例的主角，因此可以先把(B) population蝸牛口，(C)chip or fracture裂痕，台語叫『客兄』是外力引起的不是本身的構造，(D) A pattern圖案樣式，這三個跟結構無關的先刪除，所以剩下兩個，再來的話就往下看第二個線索，給到了concomitante相對應的意思，選到（Ａ），那就中招了，看似可以對應到exact mirror，但因為鏡射所在的位置有後面接的是for any disadvantage that a sinistral twist in itself could confer on its possessor is almost inconceivable.不利的條件是『不存在』這不就跟題目問的相反了（Ａ）就不對拉，再說exact mirror這是if 條件句裡面的內容，根本不是主幹，所以選項答案是他的機會會非常之小，不管看不看得懂選項（Ｅ），也只剩下他可以選了，選（Ｅ）

補充：(E) A smaller shell opening that restricts mobility and ingestion relative to that of a snail of the commoner form

先說明整個句子他不是句子他只是一組“名詞”，opening必須當名詞起始開端用，smaller shell當形容詞用，這樣在結合關係代名詞that restricts mobility and ingestion，意思就變成：有一個相對較為小的一個外殼開口端而這個開口是限制流動量及攝取量用的，接下來再接一組形容詞relative to that of.....這也是關係代名詞which is 被省略了，而前方沒有逗點研判修飾最接近的名詞，修飾前方的mobility and ingestion因為有並列所以我這兩個名詞一起看，而那個that代名詞是誰就要往前在找了，relative to有『對等』含義在，而剛剛用過的名詞mobility and ingestion已經和that restricts mobility and ingestion組成關係代名詞的不完整子句了當成形容詞用，所以這情況下只能去跟opening媒合。所以，

總結：A smaller shell opening and the smaller shell opening restricts mobility and ingestion, and these mobility and ingestion is relative to a smaller shell opening of a snail of the commoner form. 殼上有一個相對來講比較小的開口這跟那個形狀較為普通的（右旋）蝸牛他們的開口一樣都是用來限制流動量及攝取量用的。所以抓主幹是開口這也就是concomitantstructural features的具體說明，這方面是因為要符合題目要求的disadvantage，題目問的是『稀有品種的不利情況』，然後再搭配關鍵句的句子是在But left- and right-handed snails are not actually true mirror images of one another. 這個區塊上，而他的暗示是對It would seem unlikely that evolution should discriminate against sinistral snails if sinistral and dextral snails are exact mirror images, for any disadvantage that a sinistral twist in itself could confer on its possessor is almost inconceivable.這個東西取反，也就是紅色部分要變成likely and compelling，轉個彎意思就是不要跟一般普通品種一樣，而（Ｅ）選項講的是commoner form具有的特徵，那基於這串邏輯是commoner form＝（-）rarer form，所以只要是commoner form的特徵對於rarer form來說都是disadvantage。

2.The second paragraph of the passage is primarily concerned with offering possible reasons why

(A) it is unlikely that evolutionary mechanisms could discriminate against sinistral snails

(B) sinistrality is relatively uncommon among snail species

(D) a theory based on a developmental mechanism inadequately accounts for the predominance of dextrality across snail species

(E) dextral snails breed more readily than sinistral snails, even within predominantly sinistral populations

解題：

題目問why就是修辭目的題，探討句間關係，而這個句間關係是因果關係，因為這reasons why兩個字，所以目光轉向剛剛的那組套件，因為resaons有Ｓ啊，然後這組套件後方有個總結thus keeping the rare form rare去把答案生出來，或是假設只用possible看到這句Sinistral rarity might, then, be a consequence of possible disadvantages conferred by these other concomitant structural features 找到Sinistral rarity去選擇（Ｂ）只能說你矇對的，因為Sinistral rarity是結果，邏輯層次相反，而且啊，這個是屬於細節的部分，這不是考細節題，如果過度注意到這些舉例表示主幹抓太細了，好的那考點是哪呢？題目問的是找原因喔，我個人認為是在第一段尾巴的那兩個問題，因為題目primarily concerned with這是問主要傳達的訊息是...，所以題目的解讀應該是『文章的第二段整段主要是在描述一些可能的理由，為什麼要這麼做？』，也就是說必須把整個第二段封裝成一個套件，然後把這個第二段套件去跟第一段做句間關係的判讀，因此『第一段』有兩個問題必須要解答，然後是那個解答其中的keep left-handedness rare，選（Ｂ）

3.Which of the following accurately describes the relationship between the evolutionary and developmental theories discussed in the passage?

(A) Although the two theories reach the same conclusion, each is based on different assumptions.

(B) They present contradictory explanations of the same phenomenon.

(D) The second theory demonstrates why the first is valid only for very unusual, special cases.

(E) They are identical and interchangeable in that the second theory merely restates the first in less technical terms.

解題：

第四段開頭，剛剛也看過了，兩者事主從關係

Here, the evolutionary theory must defer to a theory based on an explicit developmental mechanism that can favor either right- or left-handedness.

根據結構圖顯示，ＥＤＭ是對的，ＥＶＯ不對，所以兩者關係取反，等等選項必須有『反』的邏輯詞存在，而且是建立在ＥＤＭ強壓ＥＶＯ的情況，必須ＥＤＭ>>ＥＶＯ，不然那個defer to就白搭了，選（Ｃ）

補充：像（Ａ）the same（Ｅ）identical and interchangeable就露餡拉，（Ｂ）沒有表示出ＥＤＭ>>ＥＶＯ，（Ｄ）邏輯相反了，是證明前一個有缺陷invalid才對。

4.It can be inferred from the passage that a predominantly sinistral snail species might stay predominantly sinistral for each of the following reasons EXCEPT for

(A) a developmental mechanism that affects the cell-division pattern of snails

(B) structural features that advantage dextral snails of the species

(D) anatomical incompatibility that prevents mating between snails of opposing hands within the species

(E) geographic separation of sinistral and dextral populations

解題：

推理題先來找對象a predominantly sinistral snail species might stay predominantly sinistral，他的對比對象是在第三段的：

But this evolutionary mechanism combining dissymmetry, anatomy, and chance does not provide an adequate explanation of why right-handedness should have become predominant.

這裡可以看到左VS.右的同屬性對比對像，而右旋獨大代表左旋劣勢，因此兩者間關係是邏輯取『反』的，接著看到右旋獨大的內容為：

this evolutionary mechanism combining dissymmetry, anatomy, and chance does not provide

取反之後左旋獨大的內容要是this evolutionary mechanism combining dissymmetry, anatomy, and chance does provide，所以現在目標找到對this evolutionary mechanism肯定的即可，而剛剛在畫結構圖之前，已經先認清這組代名詞是服務某三組舉例，分別為上一段的

Sinistral rarity might, then, be a consequence of possible disadvantages conferred by these other concomitant structural features.對（Ｂ）

In addition, perhaps left- and right-handed snails cannot mate with each other, having incompatible twist directions.對（Ｄ）

來看(B) structural features that advantage dextral snails of the species，有利於這群左璇的少數族群當中右旋蝸牛他們的結構特徵，不等於『由這些其他相伴隨的結構特徵的缺陷』，一個主詞是features加上關代，一個是disadvantages加上關代，光看文法就知道他們不是講同一件事情了。選（Ｂ）

補充：

EXCEPT考題，幾乎都是出在並列結構的考點上，所以目標應該關注在combining dissymmetry, anatomy, and chance這三個上面，假設如果用排出法去看（Ａ）的話，沒錯是可以選到答案，可是光定位到EDM再去判斷EDM可以決定左跟右，既然可以決定左跟右也就是可以確保左旋可能獨大，那這樣的話在考場解題時間就太慢了，馬車變南瓜了，為了確定（Ａ）是對的必須要看兩句話，才解決一題的一個選項，結果還有四個選項還沒排除，這成本真的很高。

5. In describing the "evolutionary mechanism" (the first sentence of the third paragraph), the author mentions which of the following?

(A) The favorable conditions for nurturing new offspring

(B) The variable environmental conditions that affect survival of adult snails

(D) The structural identity of offspring to parents of the same hand

(E) The frequency of unions between snails of different species

解題：

combining dissymmetry, anatomy, and chance就是這三個其中一個，availability of potential mates＝chance，選（Ｃ）

6. According to the passage, which of the following is true of Lymnaea peregra?

(A) Handedness within the species was at one time equally distributed between left and right.

(B) Under laboratory conditions, dextral eggs from Lymnaea peregra can be artificially induced to develop into sinistral snails.

(D) Handedness in Lymnaea peregra offspring is determined by two parents together.

(E) fewer sinistral offspring in dextral broods than dextral offspring in sinistral broods

解題：

問到ture基本上就幾乎是要針對ＬＰ的內容全看了，但是這裡不仿針對ture來分析看看是否還有更快得做法，因為ture這個字在論文（argument= premises + conclusion）中扮演的角色，往往會跟結論溝再一起，結論的定義就是：對於文章中一個句子的描述，作者認為永遠是『對的』。不只是結論具有此特徵，觀點也是，作者的觀點是啥，也是在說明作者所認為是對的事情，所以我們要找的東西應該是朝概念性質去著手，再來何謂前提，前提就是陳述的句子是用來支持結論的，以確保結論的保真性，不是沈葆楨，是讓結論確保永遠是對的，所以前提在論文所扮演的角色是類似舉例說明解釋的功能，根據這個原則我們往ＬＰ的內容去看找到很像是結論的句子，不一定要有個thus或是finally這類的副詞所帶出的句子，因為這樣就會上當定位到：Thus the path to a solution to the puzzle of handedness in all snails appears to be as twisted as the helix itself.這是對於整個文章的結語，不是對ＬＰ這種蝸牛的結論或觀點，哇完了～～難道要用排除法了嗎？非然也，回來結構上，有說到LP的內容是發生在第三段和第四段，ＬＰ在文章是做舉例用的，所以會支持該段主旨，而他們不管拿出什麼東西來解釋都有強調sinistral rarity. 因此選（Ｅ）

以上筆記供大夥參考若有錯誤再煩請指教