四六级命题语料的选材原则是：
　　题材广泛，包括人文科学、社会科学、自然科学等领域，但所涉及的背景知识应为学生所了解或已在文章中提供；
　　体裁多样，包括叙述文、说明文、议论文等；(三种文体，也是大家平时阅读和写作最经常练习的)
　　仔细阅读篇章难度适中，快速阅读、听力、改错和完型填空的篇章难度略低；
　　词汇范围不超出《教学要求》中较高要求的词汇，超出该范围的关键词汇，影响理解时，则以汉语或英语释义。
　　看了这几条四六级考试的命题原则后，相信大家都稍稍松了一口气。
　　既然四六级考试命题的语料均选自英文原版材料，那我们有必要了解一下英语语料的特点。(主要从不同于汉语的方面来给大家介绍)
　　英语是非常注重逻辑明确的语言。英语注重文章的实质内容，讲究层层推导、表达透彻，主题和主题句处于文章非常显要的位置。如每一段的开头或者结尾，在主题句之后，总有具体和细致的举例、说明和阐释来进一步深化主题，丰富内容。
　　我们先来看一下受汉语思维和表达影响很深的一篇作文：
　　From the picture, we can see that a beautiful American girl is in traditional Chinese costume and is smiling, as if she was asking us, “Am I like a Chinese” and speaking, “ I wish Chinese people happy like me。” It shows that with the faster pace of globalization, cultural differences are shrinking。
　　Over the ages, our Chinese people have been looked down upon by foreigners. But now, they are interested in our culture, wearing our clothes. What a change! It shows that we are getting stronger and more influential. It shows that Chinese people really stand up. In this respect, what reasons do we have to look down upon ourselves, our glorious culture and long traditional?
　　With the reform, China now is becoming a great country. She is going international. Her culture, both traditional and modern, will exercise an impact on the world. Let us work hard and make that possible in the nearest future。
　　上面的文章虽然分为三段式，但每一个段落差不多都是情绪激昂的口号，没有实质性的内容，更无严密的说理和论述。这样的短文，虽然语法上并不重大差错，但因为内容空洞、缺乏逻辑而不能得到一个好的分数。
　　我们再来看一下，同样的题目，比较符合英文思维方式和表达方式的作文是怎样的：
　　⑴The American economic system is organized around a basically private-enterprise，market-oriented economy in which consumers largely determine what shall be produced by spending their money in the marketplace for those goods and services that they want most. ⑵ Private businessmen, striving to make profits, produce these goods and services in competition with other businessmen; and the profit motive, operating under competitive pressures, largely determines how these goods and services are produced. ⑶Thus, in the American economic system it is the demand of individual consumers, coupled with the desire of businessmen to maximize profits and the desire of individuals to maximize their incomes, that together determine what shall be produced and how resources are used to produce it。
　　⑴An important factor in a market-oriented economy is the mechanism by which consumer demands can be expressed and responded to by producers. ⑵In the American economy, this mechanism is provided by a price system, a process in which prices rise and fall in response to relative demands of consumers and supplies offered by seller-producers. ⑶If the product is in short supply relative to the demand, the price will be bid up and some consumers will be eliminated from the market. ⑷If, on the other hand, producing more of a commodity results in reducing its cost, this will tend to increase the supply offered by seller-producers, which in turn will lower the price and permit more consumers to buy the product. ⑸Thus, price is the regulating mechanism in the American economic system。
　　⑴The important factor in a private-enterprise economy is that individuals are allowed to own productive resources(private property)， and they are permitted to hire labor, gain control over natural resources, and produce goods and services for sale at a profit. ⑵In the American economy, the concept of private property embraces not only the ownership of productive resources but also certain right, including the right to determine the price of a product or to make a free contract with another private individual。
　　这篇文章的第一句就开门见山，明确了主题，提出美国经济制度的特点是通过私有企业和市场导向调节作用。围绕这一主题，文章的三个段落层层展开，环环相扣，每一段落各有侧重。
　　第一段是讲私有企业受盈利动机驱使进行生产和服务，这一动机决定企业的生产和服务方式，但更重要的是，这一动机取决于消费者的需求和愿望，即市场导向。这一段的最末一句是该段的段落主题句，实际上也是全文中心思想的另一种表述方式。
　　第二段开头一句是该段的段落主题句，说明市场导向型经济的重要特点之一是它有一个价格机制，价格的上涨和下跌反映并调节消费需求。围绕这个主题句，第(2)、(3)、(4)句进一步阐述产品供需与价格浮动和消费需求的关系。
　　第三段的主题句也是该段的第一句，说明私有制企业的重要特色。该段的第二句是对主题句的进一步阐释。