· 主题句通常为首句；
· 行文套路：总分结构

3、现象解释型

· 判断标志：
a. 首段给出一个自然的或社会的现象，往往很古怪，下文对其做出解释。
b. 文章前半部出现phenomenon，文章中部出现to explain ,interpret文章后半部评论出现 explanation interpretation
范文节选：
    Historians of women's labor in the United States at first
  largely disregarded the story of female service workers
  -women earning wages in occupations such as salesclerk.
  domestic servant, and office secretary. These historians
 (5) focused instead on factory work, primarily because it
   seemed so different from traditional, unpaid "women's
   work" in the home, and because the underlying economic
   forces of industrialism were presumed to be gender-blind
   and hence emancipatory in effect. Unfortunately, emanci-
 (10) pation has been less profound than expected, for not even
   industrial wage labor has escaped continued sex segre-
   gation in the workplace.
 To explain this unfinished revolution in the status of
   women, historians have recently begun to emphasize the
( 15) way a prevailing definition of femininity often etermines
   the kinds of work allocated to women, even when such ……

范文点评：
文章开始说出了一个现象：“工厂里的女工也没有逃脱性别隔离”，第二段试图解释这一现象。

· 主题句一般是作者给予正评价的解释。
· 行文套路：phenomenon---explanation---author’s attitude
· 阅读重点： 作者的态度评价

范文
A mysterious phenomenon is the ability of over-water migrants to travel on course. Birds, bees, and other species can keep track of time without any sensory cues from the outside world, and such “biological clocks” clearly contribute to their “compass sense.” For example, they can use the position of the Sun or stars, along with the time of day, to find north. But compass sense alone cannot explain how birds navigate the ocean: after a flock traveling east is blown far south by a storm, it will assume the proper northeasterly course to compensate. Perhaps, some scientists thought, migrants determine their geographic position on Earth by celestial navigation, almost as human navigators use stars and planets, but this would demand of the animals a fantastic map sense. Researchers now know that some species have a magnetic sense, which might allow migrants to determine their geographic location by detecting variations in the strength of the Earth’s magnetic field.

范文点评：
 文章一开始就提出一个神秘现象：“鸟类按固定路线飞行”，接下去提出了“生物钟”这种解释，结果作者用But否定了；然后又提出“天文导航”，同样作者也用but否定了；最后作者又提出“磁场感觉”，基本得到了作者的肯定。