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第十八單元 推展段落方法之九——因果法（Ⅱ）

18．1原因法

有時，一個結果會源于幾個原因。同樣，段落可或以結果開頭或以結果結束，作者可以從熟悉到不熟悉的原因逐一分析，或是從分析一個又一個讀者不熟悉的原因開頭，最后引出讀者熟悉的結果。選用哪一種，決定于作者認為哪一種更有說服力。

示范段落18-1

Several changes have brought wild animals to the cities．Foremost is，that air and water quality in many cities have improved as a result of the 1970's pollution control efforts．Meanwhile，rural areas have been built up，leaving many animals on the edges of suburbs．In addition，urban wildlife refuges have been created．The Greater London Council last year spent ＄750,000 to buy land and build 10 permanent wildlife refuges in the city．As a result，many big birds are now living in the city．For peregrine falcons cities are actully safer than rural cliff dwellings．By 1970 the birds had died out east of the Mississippi because DDT had made their eggs too thin to support life．That year，scientist Tom Cade of Cornell University began raising the birds for release in cities，for cities afforded plentyof food．

18．2 示范段落分析

主題句：Several changes have brought wild animals to the cities．

因果模式（Cause-effect Pattern）：

結果（Effect）：wild animals back to the cities

原因（Causes）： 1．Air and water quality have improved．

2．Rural areas have been built up．

3．Urban wildlife refuges have been created．

18．3 因—果—因法

有時候，一個原因也許會引起一個結果，這個結果又成為另一個結果的原因，如示范段落18-2所示。

示范段落18-2

For some time now，medical scientists have noted an alarming increase in disease of the heart and circulation among people who smoke cigarettes．It has been found that the presence of nicotine in the blood stream causes blood vessels to contract，thus slowing circulation，which eventully leads to hardening of the arteries．As the arteries stiffen，less blood reaches the brain，and the end result of this slowdown is the cerebral hemorrhage，commonly referred to as a“stroke”．In addition，nicotine in the bloodstream reduces the ability of the hemoglobin to release oxygen，resulting in shortness of breath．The lack of oxygen forces the heart to beat faster—that is，the pulse rate increases—and in turn accelerates the risk of heart attack．

18．4．示范段落分析

因-果-因模式（Cause-Effect-Cause Pattern）：

Smoking tobacco→nicotine in the blood streams

→the blood vessels constract…

18．5 關于寫因果段落的建議（續）

3）著重分析直接的、明顯的原因

每個結果都有無數的原因，同樣，每個行為都會導致無數的結果。因果段落應只著重分析直接的、明顯的原因，忽略間接的原因。例如，一個學生成績不好，直接原因是沒有認真學習，間接原因也許是對學校不滿。顯然，我們應該著眼于直接的原因而摒棄間接的原因。

4）根據重要性或熟悉程度排列細節（見第19單元）

5）使用適當的排列符號（listing signals）（見第34單元）

Exercise 18-1

Directions：Read the following paragraph of cause and effect，adding suitable listing signals and linking expressions．

There are many reasons why languages change．____，

various languages that started from the same parent developed their own uniqueness after groups of speakers drifted away from one another to establish isolated，independent communities．________is the independence of and interaction with foreign cultures，often as a result of military conquest．________is rapidly expanding technologe and new systems of communication that bring all cultures and languages into close contact，with borrowing between languages a common phenomenon in the contemporary world．All languages change as the experiences of their speakers change．

Exercise 18-2

Directions：Write a paragraph analyzing the causes of students cheating on exams．

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