The success of fluoride in combating dental decay is well established and, without a doubt, socially beneficial. However, fluoride's toxic properties have been known for a century. In humans excessive intake (for adults, over 4 milligrams per day) over many years can lead to skeletal fluorosis, a well-defined skeletal disorder, and in some plant species, fluoride is more toxic than ozone, sulfur dioxide, or pesticides.
Some important questions remain. For example, the precise lower limit at which the fluoride content of bone becomes toxic is still undetermined. And while fluoride intake from water and air can be evaluated relatively easily, it is much harder to estimate how much a given population ingests from foodstuffs because of the wide variations in individual eating habits and in fluoride concentrations in foodstuffs.
1. The passage suggests that it would be easier to calculate fluoride intake from food if
(A) adequate diets were available for most people.
(B) individual eating habits were more uniform
(C) the fluoride content of food was more varied
(D) more people were aware of the fluoride content of food
(E) methods for measuring the fluoride content of food were more generally agreed on
2. One function of the second paragraph of the passage is to
(A) raise doubts about fluoride's toxicity
(B) introduce the issue of fluoride's toxicity
(C) differentiate a toxic from a nontoxic amount of fluoride
(D) indicate that necessary knowledge of fluoride remains incomplete
(E) discuss the foodstuffs that are most likely to contain significant concentrations of fluoride
For the following question, consider each of the choices separately and select all that apply
3.The passage suggests which of the following about the effect of fluoride on humans?
(A) The effect of fluoride intake from water and air is relatively difficult to monitor.
(B) An intake of 4 milligrams over a long period of time usually leads to a skeletal disorder in humans.
(C) An intake of slightly more than 4 milligrams for only a few months is not likely to be life-threatening.
結構分析：
開頭的兩句話直接點出主角F這個化學物質，不理她是啥，however前方是好處beneficial，後方是toxic，所以作者對於Ｆ是抱持著不好的態度，接著往下一段看，開頭直接給你個questions，後方直接出現舉例的訊號字，等於是文章到此發展結束，作者對於Ｆ是沒啥好印樣的，作題吧～～啊等等結構圖生一下好了。
1. The passage suggests that it would be easier to calculate fluoride intake from food if
(A) adequate diets were available for most people.
(B) individual eating habits were more uniform
(C) the fluoride content of food was more varied
(D) more people were aware of the fluoride content of food
(E) methods for measuring the fluoride content of food were more generally agreed on
解題：
關鍵字在easier to calculate fluoride intake from food，所以找到文章的尾巴
And while fluoride intake from water and air can be evaluated relatively easily, it is much harder to estimate how much a given population ingests from foodstuffs because of the wide variations in individual eating habits and in fluoride concentrations in foodstuffs.
好的材料有了，接下來找廚師下菜，因此推理題開始啟動對比對象招式，一個輕鬆一個配困難，所以會發現文章內容的後半段給出harder to estimate，那個就是對比對象拉，很明顯的兩邏輯是相反的，所以等等把感到困難的內容去反之後，就是答案了，往後看到because of the wide variations in individual eating habits and in fluoride concentrations in foodstuffs.在兩個領域（飲食習慣和Ｆ殘留量）當中他們是變化多端的，所以取反，一成不變，選（Ｂ）
2. One function of the second paragraph of the passage is to
(A) raise doubts about fluoride's toxicity
(B) introduce the issue of fluoride's toxicity
(C) differentiate a toxic from a nontoxic amount of fluoride
(D) indicate that necessary knowledge of fluoride remains incomplete
(E) discuss the foodstuffs that are most likely to contain significant concentrations of fluoride
解題：
第二段功能是點出問題在哪，後面是舉例從for example開始，那他的邏輯理所當然延續著到底是啥問題，因此要找個選項『充滿問號』不確定的才行，其中（Ａ）要小心那個doubts確實有朦朧美，但是第二段跟第一段中間沒有轉折字眼，所以文章的總邏輯還是順著however的toxic走的，因此（Ａ）反而跟我們要找東西相反。（Ｂ）是肯定語氣，一口咬定toxicity就是問題，這樣跟第二段開頭的questions remain有衝突。找到（Ｄ）incomplete，選（Ｄ）
For the following question, consider each of the choices separately and select all that apply
3.The passage suggests which of the following about the effect of fluoride on humans?
(A) The effect of fluoride intake from water and air is relatively difficult to monitor.
(B) An intake of 4 milligrams over a long period of time usually leads to a skeletal disorder in humans.
(C) An intake of slightly more than 4 milligrams for only a few months is not likely to be life-threatening.
解題：
推理題，又配上多選題，只能一個一個對應了，然後推理題的特性要注意到對比對象，所以看到
(A) The effect of fluoride intake from water and air is relatively difficult to monitor.
可以對應到原文，And while fluoride intake from water and air can be evaluated relatively easily,完全相反，而且沒所謂推理題的考點邏輯存在，這根本是『是非題』的選項，文章跟選項文字連連看就有答案，這不是推理題啊
(B) An intake of 4 milligrams over a long period of time usually leads to a skeletal disorder in humans.
(C) An intake of slightly more than 4 milligrams for only a few months is not likely to be life-threatening.
（Ｂ）（Ｃ）的共同點是4 milligrams，那就一起看吧，對應到
In humans excessive intake (for adults, over 4 milligrams per day) over many years can lead to skeletal fluorosis, a well-defined skeletal disorder, and in some plant species, fluoride is more toxic than ozone, sulfur dioxide, or pesticides.
答案就是over many years (文章)VS.only a few months（Ｃ），邏輯取反，因此lead to skeletal fluorosis取反，變成不會造成氟中毒，選（Ｃ）
補充：
那（Ｂ）錯的原因是以偏概全，skeletal fluorosis, a well-defined skeletal disorder，這意思是氟中毒是『一種』skeletal disorder。
以上筆記供大夥參考若有錯誤再煩請指教
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