我们来通过TPO16的Trade and Ancient  Middle East 探讨下这类文章的特点。

文章首段一二两句出现这样的内容：

Trade was the mainstay of the urban economy in the Middle East, as caravans negotiated the surrounding desert, restricted only by access to water and by mountain ranges. This has been so since ancient times, partly due to the geology of the area, which is mostly limestone and sandstone, with few deposits of metallic ore and other useful materials.

首先提出贸易对中东来说很重要，第二句说明原因没有铁矿和原材料。之后第三句开始都是举例说明这一情况算是细节了。

紧接着第二段首句就是：

Reliance on trade had several important consequences.

直接展开依赖贸易所产生的结果，我们就可以预判下文啦，通过往下细读，会发现二段展开的内容是讲生产关系中主人和工匠的关系非常和谐平等～

而三段开头This mode of craft production favored the growth of self-governing and ideologically egalitarian craft guilds everywhere in the Middle Eastern city.说明和二段关系非常紧密，继续讲二段提到的这种生产关系发展壮大成独立平等的协会。

这样就得知二三两段是依赖贸易所产生的第一个结果：手工生产关系中人与人是和谐平等的，促进了独立平等的手工协会的发展。

接着四段开头：

The mercantile economy was also characterized by a peculiar moral stance that is typical of people who live by trade-an attitude that is individualistic, calculating, risk taking, and adaptive to circumstances.

这样便交代了依赖贸易所产生的第二个结果，也就是这种商业经济下衍生了一系列比较好的道德品质。

然后五段开头：

Dependence on long-distance trade also meant that the great empires of the Middle East were built both literally and figuratively on shifting sand.

首句主旨句表达依赖贸易就像这个国家是建立在流沙之上的，言外之意依赖贸易产生的第三个结果：国家是不稳定的。随后两点通过moreover连接国家不稳定的两个方面，也就是两个分论点。

这样全篇文章的框架就非常清晰啦，非常有助于我们判断出题点，轻松拿捏解题要点，读起来前后连贯，减少很多学生的阅读障碍。类似这种现象解释类的文章还有TPO40：Latitude and Biodiversity 现象—原因类、TPO 54: the Commercialization of Lumber 现象—原因类等，感兴趣的同学们可以去做题感受一下～