很多考生不知道在做 GMAT 邏輯推理中的假設題型時，應該如何有效找到可以使得整個推理成立的必要條件，或者考生往往出於使推理一定正確的心理，在各個選項中遊走不定，最終導致考生無法清楚到底哪個選項才是 " 真正 " 的符合題幹要求的推理條件。其實我們在解題的過程中需要把握一個宗旨，也許我們就會發現其實假設題型並非我們想象的那樣難。下面是小編為大傢整理的一些具體實例。
無法找出題幹中討論對象之間的本質關系
例：A thorough search of Edgar Allan Poe ’ s correspondence has turned up not a single letter in which he mentions his reputed morphine addiction. On the basis of this evidence it is safe to say that Poe ’ s reputation for having been a morphine addict is undeserved and that reports of his supposed addiction are untrue.
Which of the following is assumed by the argument above?
( A ) Reports claiming that Poe was addicted to morphine did not begin to circulate until after his death.
( B ) None of the reports of Poe ’ s supposed morphine addiction can be traced to individuals who actually knew Poe.
( C ) Poe ’ s income from writing would not have been sufficient to support a morphine addiction
( D ) Poe would have been unable to carry on an extensive correspondence while under the influence of morphine
( E ) Fear of the consequences would not have prevented Poe from indicating in his correspondence that he was addicted to morphine.
上述題幹中提到：一、研究發現 Poe 的信件中未提及他患有嗎啡癮 ; 二、Poe 沒有嗎啡癮
本題極力在讓考生從 " 對 Poe 的信件調查 [ 證據 ] → Poe 未患有嗎啡癮 [ 結論 ] " 找出兩者的內在聯系，5 個選項中也給出瞭不同的假設，那麼我們隻需通過反推，來找出一種能夠使得推理成立的假設條件即可，但考生往往會拋開 " 信件調查 " 去思考其他使得上述結論正確的條件 ( 假設 ) ，換句話說考生往往會認為除瞭對信件的調查這樣一個證據以外，還可以有其他證據能夠推出 Poe 未患有嗎啡癮。通常來講，當一個推理是從一個我們已知的，已經發生的事實推斷出一個結論的時候，我們需要記住的就是，其中的隱含假設多為這個結論的唯一原因，換句話說，在本題中要想對 Poe 的信件做出說明，那麼我們隻能假定 Poe 不會因害怕後果而不在其信件中提及對嗎啡的嗜好，本題的正確假設選項為 E.
無因就無果
在假設題型裡，如果想要找出段落推理的一個必要條件，那麼我們首先就應明確，這個必要條件就是使得推理必然成立的一個假設，假設必為支持性假設。
例：
The population of peregrine falcons declined rapidly during the 1950 ’ s and 1960 ’ s and reached an all-time low in the early 1970 ’ s. The decline was attributed by scientists to the widespread use of the pesticide DDT in rural areas
Which of the following, if true, gives the strongest support to the scientists ’ claim?
( A ) DDT was not generally in use in areas devoted to heavy industry
( B ) In the time since the use of DDT was banned in 1972, the population of peregrine falcons has been steadily increasing
( C ) Peregrine falcons, like other birds of prey, abandon eggs that have fallen out of the nest, even if the eggs remain intact
( D ) Starlings, house sparrows, and blue jays-birds the peregrine falcon preys on were not adversely affected by DDT in their habitats
( E ) Other birds of prey, such as the osprey, the bald eagle, and the brown pelican, are found in the same areas as is the peregrine falcon.
題幹是由果推因，遊隼數量下降由使用殺蟲劑 ( DDT ) 所致，我們不妨將 " 遊隼數量下降 " 視為 B, 而將 " 使用 DDT" 視為 A, 如果由 B → A 正確 , 那麼我們就可以得出沒有 A 就不會存在現在的 B, 因此我們就可以推斷兩種情況，DDT 禁用前與 DDT 禁用後遊隼在數量上的比較，如果在 DDT 禁用後，遊隼數量開始增加的話，那麼我們就會非常肯定的是確實是殺蟲劑的使用導致瞭遊隼數量的減少。這種類型的題目出錯的主要原因有兩點：一：考生無法把握題幹要求，在段落內容之外進行推理 ; 二：無法將題幹給出的原因視做唯一原因。
小編建議大傢能在平時的不斷練習的過程中，學習找出論點和結論的能力，並依據兩者的關系進行判斷，隻要弄清論點和結論也就相當於找出瞭答案。在實踐練習中，大傢也應善於從題幹所描述的對象中找出核心關鍵詞語，一般來講，我們可以通過在選項中加入 Not 來判斷推理成立的有效性並排除那些誤選項。
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