說明文是用說明的表達方式來解說事物、闡明事理的文章，以解釋、闡述事物的形狀、特征、性質、成因、關系、功能、作用為目的。而說明是對事物的發生、發展、結果、特征、性質、狀態、功能等進行解釋、介紹、闡述的一種基本表達方式。

可用于事物說明的寫作手法很多， 鑒于六級寫作的趨勢，這里著重介紹四種類型的說明文。
1. 舉例說明文
通過舉例或列舉闡明事理的寫作方法。為使讀者弄清某一事理，或使抽象化概念形象化或具體化，作者拿出文章的較大篇幅 進行舉例說明，以進一步證明所述道理的真實性和可行性。
2. 知識性說明文
通過解釋說明來闡明事實、道理或介紹知識、信息等的寫作手法。從整篇文章看，此類作文旨在為讀者提供并未知曉的知識和信息。讀者通過閱讀此類文章通達事理，懂得該怎么辦。
3. 對比說明文
通過對兩種事物進行對比或比較，找出兩者之間的共同點或對立點的寫作手法。為說明某一事物在不同條件下的差異，或此事物與同類或不同類事物的差別，作者往往采用比較和對比的手法來獲得分清事理的寫作效果。讀者從比較或對比說明中獲得教益。
4. 定義說明文
通過揭示概念的內涵或下定義的方式來明確概念的寫作方法。旨在給事物的性質和特點下定義，回答“什么是……”和“怎樣理解……”之類的問題。故此，這類作文要求作者具備科學嚴謹的文風，定義要下得準確合理，文字說明要全面到位。作者常常會借助舉例說明的手法或比較說明的手法達到界定事物的目的。
在實際寫作中，作者一般在同一篇文章中運用多種手法達到說明事物的寫作目的，運用單一手段者甚少。

Sample 1
The Potential of Internet Education

Internet is getting into people’s life and becoming more and more popular. Experts are now working on setting up a national long-distance educational system in China to provide educational opportunities via Internet.
In reality, the educational via Internet plan has been taking shape. Some universities have already got involved in regional long-distance education, catching the attention of many educators and computer experts worldwide. Others have just connected their campus computers for teaching and research, and provided more opportunities for learner.
The Internet education will be developing dramatically. It’s estimated that computerized long-distance teaching networks will be available by 2010 for postgraduate education, vocational programs, teachers’ training and employees’ training. Moreover, it will soon cover all the corners of the globe and eventually win the worldwide popularity.

評析：
這是篇知識性說明文。文章作者按三段式行文。首段概括說明遠程教育越來越普及而且專家們正致力于建立全國互聯網教育系統。正文說明我國互聯網教育的現狀：一些學校正普及區域性的網絡教育，引起全國關注；而另一些學校將教育和科研聯網，共同開發，機會多多，潛力巨大。文章最后展望了互聯網教育的前景，到2010年我國將基本建成遠程教育系統。從互聯網教育的發展趨勢我們可以斷定，不久互聯網教育將在世界各個角落普及。文章脈絡清晰，結構嚴謹，行文流暢，語義連貫，順理成章。

Sample 2
Directions: For this part, you are allowed thirty minutes to write a composition on the topic Good Manners in Different Cultures? You should write at least 150 words, and base your composition on the outline (given in Chinese) below:
i. 在許多社交場合一個人舉止的好壞顯得十分重要。
ii. 舉例對比說明不同文化背景下的良好舉止。
Good Manners in Different Cultures

In most cases of social contact, nothing reveals more clearly what kind of person one is than his manners. A person with good manners is more welcome anywhere than one of pleasing appearance but with unrefined manners. Yet in different cultures, there are different manners which it is considered worthwhile to cultivate in social life.
When you meet a friend on your way, for instance, it is common sense to say something like “Where are you going?” or “Where have you been?” in the Chinese culture. In Western societies, by contrast, even though both are close friends, it is good manners to avoid greeting like that, for the first reaction of most English-speaking people to such greetings would probably be “It’s none of your business!” The same is true of when a person sneezes. On that occasion, it is taken for granted that some Chinese nearby remarks, “ Someone misses you.” Or humorously” Who is cursing you?”, whereas an American or Englishman would rather like to say, “God bless you!” A guest in an Asian house, if offered something to drink, usually leaves a little to indicate that he has had enough, but in England, a gust always finishes up a drink to show that he has enjoyed it.
As for body languages, not all of them in one culture convey the same message in another culture. In China, it is normally seen as signs of affection to touch, hug or even kiss a friend’s baby. In the eyes of western mothers, on the other hand, such actions can arouse dislike and even hostility from them. The cases cited here can serve only as a reminder that one culture’s meat may sometimes be another culture’s position.

Sample 3
Directions: For this part, you are allowed thirty minutes to write a composition on the topic Computer Viruses. You should write at least 150 words, and base your composition on the outline (given in Chinese) below:
1. 目前電腦系統時常受到病毒感染。
2. 電腦病毒有許多，試舉例說出幾種。
3. 我們應千方百計殺毒。

Computer Viruses
Computer virus, whose essence component is a set of instructions, is one kind of threat to the security and integrity of computer sys tem. Nowadays computer systems worldwide are often infected by computer viruses. Some cause the loss of programs and date, erase files or subtly alter data. Others even crash computers or make them useless. In this way, each year they cause tens of billions (US$) of losses.
It’s estimated there are about 4500 kinds of computer viruses, being unleashed at the rate of about 5 per day. How terrible! A case in point is “Love Bug” which proclaims “I Love You” in the E-mail subject line. Once the Internet surfer opens the file with “I Love You”, the viruses would copy themselves and destroy valuable computer pictures and video files. Another case in point is the CIH, which is also very destructive. Besides, there are also “Tedious”, “Concept F” and “Explore Zip”, “Romeo & Juliet”, to name only a few.
However, it’s high time for us to work out effective ways to purge the viruses. On the one hand, I hope anti-bug experts would write out more bug killers such as KV 3000 so as to eliminate the bugs. On the other hand, we should enhance the cyber law and force the virus writher to stop playing pranks on the computer users so as to let the world be bug-free.

Sample 4
Directions: For this part, you are allowed thirty minutes to write a composition on the topic Cyber Crimes. You should write at least 150 words, and base your composition on the outline (given in Chinese) below:
1． 網上犯罪的形式很多，如……
2． 網上犯罪的根源。
3． 如何打擊網上犯罪現象。

Cyber Crimes

Nowadays cyber criminals seem to be everywhere, with a few clicks, committing all kinds of cyber crimes. To illustrate, some commit fraud or lift intellectual property. Others subvert deals, snatch passwords or disrupt e-commerce. Still others unleash viruses to crash computers. As a result, these hackers do a great damage to companies and computer user, causing computer losses up to 10 billion dollars per year.
Naturally, there are many causes for the cyber crimes. In addition to the wicked nature of the hackers, the frailties of Internet partially nourish the crimes. Just because there are holes in Internet-the complex soft ware is buggy and often infested, the cyber vandals can find out the weakness in the Website software programs and by manipulating software glitches, gain access to Website, committing all kinds of crimes.
However, we shouldn’t tolerate these cyber criminals any more. And it’s high time for us to take all the effective steps to battle the cyber crooks. First we should reinforce the cyber laws to protect the Web, the powerful engine of economy. Besides, we should use high techniques to improve intrusion detection, encryption and computer security. Finally, we should train more talented people to build up more firewalls so as to make the Net immune to all kinds of viruses and unassailable to all a kinds off cyber criminals.

Sample 5
Directions: For this part, you are allowed thirty minutes to write a composition on the topic Hackers. You should write at least 150 words, and base your composition on the outline (given in Chinese) below:
1. 黑客的目的。
2. 試舉例說明黑客攻擊的目標。
3. 如何打擊黑客。

Hackers
Nowadays, hackers, the terrific cyber criminals often hack into Websites for various purposes. Some malicious hackers execute assaults on computers chiefly for some evil purposes. Other profiteers make attacks on e-commerce sites chiefly for financial purposes. Still some others hit Websites either to test their skills or to tease the useless cyber experts for fun.
Hackers have various targets of their web attacks. Some super hackers can penetrate almost all the sites on the Web. And they are esp. enjoy hacking into the safest Websites and government agencies on the Web. Therefore, their first target is the Pentagon, which is “visited” by unwelcome guests for about 20,000 times a year. Interestingly enough even White House can fall victim to hacker. Other hackers aim at attacking the biggest e-commerce sites. A case in point is that Elong. com and Sina.com have been harnessed by hacker. Another case in point is that even the largest Worldwide Website Yahoo was once forced to shut down. As a result, they cause great financial losses each year.
However, it’s high time for us to take all the effective measures to hunt and battle hacker. First, we should deprive them of their tools, such as scans, sniffers etc., with which they can spot out some weaknesses on the Web and make the attacks. Besides, we should work out cyber law and enhance the law management on the Web and increase the punishment of hackers. Finally, we should further develop encryption and try to build more firewalls in order to lock the hackers out.

Sample 6
Directions: For this part, you are allowed thirty minutes to write a composition on the topic My Millennium Dreams. You should write at least 150 words, and base your composition on the outline (given in Chinese) below:
1. 千禧年之際是憧憬未來的最佳時刻。
2. 試舉例說明你有哪些千禧年的夢想。

My Millennium Dreams

The new year’s eve naturally brought me into a dream land. In spite of the controversy whether the year 2000 marks the beginning of a new century, I cherished many millennium dreams at that time.
First, I dream we’ll be living in a more beautiful, convenient, fair and secure living environment, with Internet bringing us more convenience, and globalization unprecedented prosperity in economy. I even dream that high-tech will bring us many wonders and even enable us to drive sky-cars or sky –automobiles to visit other planets in the solar system just as we visit our next door neighbors.
Second, I dream that with the successful completion of the working draft of human genome map, the life-span of all the globers will be doubled, and even tripled. And I dream that the future globers will be able to cure whatever incurable diseases.
Third, I dream, with peace and development as an irresistible trend in the 21st century all the globers will be able to live in a harmonious, peaceful and prosperous world. To sum up, I have many, many nice millennium dreams. The above mentioned are only my most wishful dreams.

Sample 7
Directions: For this part, you are allowed thirty minutes to write a composition on the topic The Significance of the First Working Draft of Human Genome Map. You should write at least 150 words, and base your composition on the outline (given in Chinese) below:
1. 人類第一張基因草圖的意義重大。
2. 試舉例說明其重大意義。
The Significance of the First Working Draft of Human Genome Map

The completion of the first working draft of Human Genome Map is of great significance in human history. It’s so important that it’s often deemed as the biological equivalent of the landing on the moon. Why?
Because, first, decoding the human genome, the secret of human life, is hailed as one of the greatest scientific milestones in the overall progress of the Human Genome Project. Besides, it’s of vital importance to the development of life science. Based on the findings of the project, our life-span might be doubled, or even tripled. Therefore, that’s why we regard the achievement as the common wealth, even the most valuable asset of the whole mankind.
Second, the sketch is of great importance to the development of medicine and pharmaceuticals. Because the great advances in understanding of human genetics can help human beings know more about themselves and how to treat the major diseases, it will enable medical industry to develop fantastically. Therefore, we have every reason to expect the greatest killers in the world, such as cancer and AIDS, will be cured in the near future.
Finally, the working draft of Human Genome Map will greatly promote the development of biological information and technology, and help lay a sold foundation for the biological industry__ the pillar industry in the 21st century.

Sample 8
Directions: For this part, you are allowed thirty minutes to write a composition on the topic Internet in China. You should write at least 150 words, and base your composition on the outline (given in Chinese) below:
1. 因特網在中國的現狀。
2. 因特網的用途。
3. 因特網的未來。
Internet in China

With the arrival of the knowledge economy age, Internet, as a new media, has come into our life. Nowadays, getting on the line and using Internet has become popular in China, especially in some big cities. Why is Internet getting so popular in such a short time?
The popularity of Internet results from its great utility. With Internet, it is convenient and fast for people to get a variety of information and what they need is just to press the key buttons. E-mail is another popular use. It can transmit your letter quickly, safely and accurately. Besides, Internet can have some other uses. Doctors may use it to diagnoses and treat their patients by discussing or exchanging experience with doctors in other parts of the world. Students may obtain new knowledge from a nation-long-distance-education-system via Internet. Finally, businessmen can conduct e-commerce or E-business on the Net.
With so many uses and advantages, there is no doubt more and more people will be wired to Internet – the information expressway. In short, with its high speed and efficiency, Internet will be more popular in China in the near future.

Sample 9
Directions: For this part, you are allowed thirty minutes to write a composition on the topic The Internet E-mail. You should write at least 150 words, and base your composition on the outline (given in Chinese) below:
1. 電子郵件開辟了新的通訊渠道且日益普及。
2. 電子郵件給我們帶來便利。
3. 電子郵件的發展前景。

The Internet E-mail

E-mail, as an entirely new way of communication by means of computers, is becoming so popular in both developing and esp. developed countries, that it’s difficult to imagine modern life without it.
E-mail is fast, inexpensive and highly efficient. It has brought much convenience to our daily life. First, you can send and receive by E-mail a variety of information and documents such as letters, papers, video and audio files to anyone in over 170 countries in a short time. Moreover, language barriers are not a problem, because the Internet software is capable of translating your mail into whatever language you want. Besides, you can also store, delete, edit, compile and search your E-mail or send it simultaneously to different places. Finally, by defining your own passwords you can always keep your mail a secret.
With the fast expansion of the band-width and wider application of Internet, E-mail will be more and more useful and soon it will become an indispensable means of communication throughout the globe.

Sample 10
Directions: For this part, you are allowed thirty minutes to write a composition on the topic Embracing the Knowledge Economy Age. You should write at least 150 words, and base your composition on the outline (given in Chinese) below:
1. 如今知識經濟初見端倪。
2. 知識在知識經濟時代中起主導作用。
3. 舉例說明你怎樣擁抱知識經濟的新時代。

Embracing the Knowledge Economy Age
The arrival of the new century has brought us a new message: knowledge economy age is fast taking shape in the world’s scale. Many new academic fields have been explored or established. Still more skills and technologies are emerging every year, every month, even every day. People are surprised to find that knowledge is really exploding at an alarming speed. All this points to the fact that knowledge economy age is rapidly approaching us.
Knowledge economy is an entirely new economic system, in which knowledge plays a dominant role. The possession, manufacture, distribution and consumption of knowledge are the basis of economic activities. Whoever possesses more and newer knowledge will become wealthy. Hence the pursuit of new knowledge will be every individual’s goal and lifelong task.
How can I better embrace the new age? As a working professional graduate, I have already realized how acute the competition will be. So I have made up my mind to make the best use of my time to learn as much knowledge as possible. Even after graduation I will do my best to update my knowledge and master all the necessary skills needed in my future career. Knowledge is strength and wealth. After all, opportunity always benefits the prepared mind.

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