of
materials that can be foundin any good library.
分类词（classifier）：kinds
列举词（listing signals）：first，second，third
分类（categories）：1.books on all subjects
2.reference
materials
3.periodicals
16.2关于如何写分类段落的建议
1）依据一个原则分类
把一事物分类后，要自始至终遵循同一分类原则。在示范段落16－1，分类原则是“the kinds of materials”。
2）所分类别必须互不包容
在示范段落16－1中，属于第一类的“books on all subjects”与属于第二类的“reference materials”界线分明.反之亦然。
3）分类必须完整
如果所分类别不完整，所作的分类则徒劳无益。如上例，所分三种“materials”应包括“all materials in a library”。
4）运用熟悉度方法排列
作者经常根据该读者对所分类别的熟悉程度排列顺序。通常先讨论读者最熟悉的，然后逐步讨论不熟悉的（关于熟悉度法见第19单元）。
5）使用分类词和列举符号
有经验的作者经常使用类词介绍概类，然后使用列举符号表明概类中的各分类。在示范段落16－1中，类词是“kind”，列举符号是“first，second，third”，下面是经常使用的类词：
kind，type，group，thought，way，class，part，element，factor，aspect，division，characteristic，subdivision，reasons，category，等等。
exercise 16-1
directions：read the following paragraph，find out the topic sentence，the classifier，and the categories.
there are three fundamental human body types—endomorphic，mesomorphic，and ectomorphic.the extreme endomorph combines
heavy fat distribution and lack of bony angularity with around face，short neck，wide hips，and heavy limbs.the extreme mesomorph has a solid
chest，slender waist，long torso，and relatively short，powerful arms and legs.extreme ectomorphs are
characterized by their slender bodies，short trunks，long arms and legs，long narrow hands and feet，and lack of fat.
topic sentence：____________________________________________
classifier：_____________
categories：________________________________________________
exercise 16－2
directions：divide the books college students often read into three kinds and
describe them one by one.
________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
exercise 16-3
directions：write a paragraph of division and catagory with the given topic
sentence and details.
topic sentence：a language is made up of many elements
details：1.sounds 2.words 3.sentences
________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
第十七单元 推展段落方法之九——因果法（1）
17.1因果法
因果法（cause and effect）段落通常回答“why？”的问题。大多数人认为在自己或别人生活中发生的事情必然事出有因，因此总要知道为什么会发生这样或那样的事情。原因（cause）指的是导致结果的发生在过去的事情，结果（effect）指的是已发生的事情将会产生的后果。
17.2结果法
解释一个原因（cause）的几个结果（effects）的段落，可能以下面两种顺序之一出现：或者以原因开头，接着指出一个一个结果，如下面示范段落17－1所示；或首先摆出结果，然后指出原因。
示范段落17－1
many people are worried about what television has done to the
generation of american children who have grown up watching it.for one thing，recent studies tend to show that tv
stifles creative imagination.some teachers feel that television has taken away the child's
ability to form mental pictures in his own mind，resulting in children who cannot understand a simple story without
visualillustrations.secondly，too much tv too early tends to cause children to withdraw from real
life experiences.thus，they grow up to be passive
spectators who can only respond to action，but not initiate it.the third area for concern is the serious complaint frequently made
by elementary school teachers that children exhibit a low tolerance for the
frustrations of learning.because they have been conditioned to see all problems resolved in
30 or 60 minutes on tv，they are quickly discouraged by any activity that promises less than
instant gratification.but perhaps the most serious result is the impact of television
violence on children，who have come to regard it as an everyday thing.not only does this increase their
tolerance of violent behavior in others，but most authorities now concede that under certain conditions，some children will imitate anti－ social acts that they witness on
television.
17.3示范段落分析
主题句：many people are worried about what
television has done to the generation of american children who have grown up
watching it.
因果模式（cause and effect pattern）：
原因（cause）：television
结果（effects）：1.tv stifles creative imagination.
2.tv causes
children to withdraw from real life experiences.
3.children
exhibit a low tolerance for the frustrations of learning.
4.children have
come to regard violence as an everyday thing.
17.4关于如何写因果法段落的建议
1）段落一开始就表明目的
在段落一开始就陈述你所关心的原因或结果是什么。例如，在示范段落17－1，主题句就把目的限定为分析“the effects of television on american children”。
2）选择主题要适中
选择太大的主题会给你带来麻烦。因此，记住要选择你可以驾驭的主题。例如：“effects
of television”作为主题会太大，难以下笔。然而把它限制为“effects on american children”就容易多了（第18单元继续讨论因果法）。
exercise17－1
directions：write a paragraph，analyzing the effects of students cheating on exams.
______________________________________________________________________________________________________________