能根据表达的内容使用不同的句子结构，会产生较好的艺术效果。 4. 多样性
多样性指的是句子形式的多样化。即句子长短、结构、类型等的多样性。句子的多样化是为作文增色的有效手段。为了使文章更具有吸引力，就要避免全文使用结构相同、长度相近的句子。全文只有一、两种句式并且长度大致相等，会使文章变得单调、呆板、说服力不强。因此，若想使文章语言生动，就必须注意长句和短句、简单句和并列句、复合句的交替使用。
试比较以下两段文字，注意体会其中因句法变换所带来的效果。
1) A career is not easy to choose. It is one of the most important decisions you will make in your life. Find the right career, and you will be happy and successful. Find the wrong career, and you will be unhappy and unsuccessful. You should explore your choice of occupation from every angle. You should collect as much information as you can. You should try different kinds of jobs before making your final decision. You should evaluate yourself. You should make sure of your own interests.
2) For most people, choosing a career is not easy. And it is one of the most important decisions you have to make in your life. If you can find the right career, you are more likely to live a happy and successful life; if not, you will probably have to face a lot of trouble. It pays, therefore, to explore your choice of occupation from every angle, collect as much information as you can, and even try different kinds of jobs before making up your mind. Above all, evaluate yourself. Be sure where your interests are.
要想使句子多样化，我们可以通过改变句子的结构，改变句子的长度，改变句子的主语以及运用修辞格等方法获得。然而在追求多样化的时候，我们一定要明白，句子的多样化只是我们写作的一种手段而不是目的。究竟采用什么样的句子结构和形式应由文章的体裁和中心思想来决定。我们不能舍本逐末，忽视意义表达的连贯而片面追求句式的丰富。
第二节 段落发展技巧
段落是若干相关的句子围绕一个中心思想或为表达一个统一的主题组合在一起的写作单位。段落由若干个句子组成，通常表达一个中心思想。因此，段落不能由一组句子随意堆砌而成，即不能把毫不相干的思想或观点放在一个段落。而是应当符合一定的模式和具有某些基本特征，并遵循一定的段落发展方法。一段好的文章应具有完整性、统一性和连贯性。要写出一篇好的文章，必须写出好的段落，这是毫无疑问的。很多考生看着作文题目和列出来的提纲，感到无话可说；勉强想出来补充说明提纲的句子却与提纲联系不紧密，且句与句之间逻辑关系混乱，有明显的凑字数的痕迹。不知怎样展开段落，是大多数考生在四级考试作文时遇到的难题。要成功地展开段落，首先必须了解段落的基本结构。 一、段落构成3要素
段落由句子组成，根据段落中各句的地位及其相互关系，可以将段落中的句子分成：主题句、扩展句和结尾句。 1. 主题句（topic sentence）
主题句点明段落的中心内容，并限制段落展开的范围。主题句是段落的灵魂，读者可以从主题句上明了全段的中心意思。因此，考生在写作文的时候，必须围绕主题句展开段落。同样，要想写好段落必须写好主题句。 1) 主题句的位置
主题句可以出现在文章的开头、段落中间、段落结尾处。对于四级考生来说，我们建议最好先想好主题句，并把主题句放在段落的开头，这样可以提醒考生围绕主题句展开段落，
避免离题，同时也让阅卷老师一目了然。
写出好的主题句是写好段落的基础。我们看下边这段文字：
There are many advantages in doing a part-time job for a college student. First, a part-time job enables you to earn some pocket money, thus makes you become more independent of your family. And with the money you have eared you can buy books, clothes, food, etc. Secondly, a part time job offers you an opportunity to apply what you have learned in school into practice. Thirdly, a part-time job helps you to gain social experience which will be helpful in your future job and make yourself adaptable to the society.
这段文章的主题句就是第一句话，点出该段的中心意思：做兼职工作对一个大学生有许多好处。接下来又从三方面围绕主题句展开论述，三方面紧扣主题，衔接严密，可以说这一段落是一个中心思想明确、论述充分的好段落。 2) 主题句的写法
因为主题句在段落中是总结性的句子，它必须具有较强的概括性，能够概括整段内容。根据题目或提纲所写出的好的主题句应该能够起到“画龙点睛”的作用，但它不能太空洞，必须有明确的主题思想；同时，它也不能太琐碎，否则就无法进一步发展下去。这是我们写主题句的时候应该注意的。如：
例1：Women are playing an increasingly important role in China. . 例2：Sports become more and more popular.
例3：Sports can make us healthy both physically and psychologically. 例4：Today more and more women are going out to work.
例1把主题限制在中国，涉及面适度，有概括性，可以用作段落的主题句。 例2范围太广，太空洞，应该再具体一些。 例3 则又太具体，使段落没有扩展的余地。 例4把描写细节的句子作为主题句，主题句涉及的面太窄，没有展开讨论的余体。因此，描写细节的句子不能作为主题句。 2. 扩展句(supporting sentence)
确定了主题句之后，我们就需要用扩展句来说明、支持主题句，使读者感觉主题句更有说服力。扩展句是段落主题句的延伸和发展，起着辅助主题句、扩展段落中心的作用，对主题句的中心思想或者举例说明，或者详细解释和论证。一般来说，一个段落会有若干个扩展句。根据在段落中的地位，这些扩展句通常可以分为一级扩展句和二级扩展句。一级扩展句直接为主题句服务，二级扩展句直接为一级扩展句服务，起补充说明的作用。以此类推，三级扩展句是直接支持二级扩展句。
比如：
Science can do good to mankind, but it can do evil as well. When it is wisely used, it will bring benefit. For example, atomic energy can help us generate electricity. However, if it is wrongly used, its destructive power is uncontrollable and terrible. It can destroy thousands and thousands of lives in a split second.
在这个段落里，第一句是主题句，第二句和第四句是一级展开句，第三句和第五句是二级展开句。
扩展句是用来体现段落的主题思想的，因此不可含糊其词、言之无物，而要清晰、详实；同时扩展句要由较强的说服力，能清楚地表达思想，绝不可只凑篇幅、凑够字数了事。
为了清楚地表达思想，扩展句必须层次分明、意义连贯，并围绕主题句展开，为主题句服务。与主题句无关的扩展句不仅“画蛇添足”，还能破坏主题句的中心位置，使段落显得零散。先说什么，后说什么，应有个合理的安排。也就是说，上一句要为下一句铺平道路，
下一句是上一句的自然延伸，一步一步地论证或叙述主题。就四级学生写作而言，每句话的平均长度最好应控制在10-15个词为宜。当然，随着写作水平的提高，句子的长度可相应增加。
3. 结尾句（concluding sentence）
所谓结尾句就是总结段落的句子，它在段落中起着非常重要的作用，它用一句话将段落内容进行归纳总结，对全段中心思想做出精炼的浓缩。写好结尾句对整个段落来说是至关重要的。一个段落的结尾句写得不好，会使整个段落看上去虎头蛇尾。因为段落的内容是说明主题的，因此结尾句和段落主题句相呼应，或者说是主题句的再现，并与扩展句相关联。结尾句用来总结段落，进一步强调和深化段落的主题。有时候结尾句还能起到承上启下的作用，使前后两个段落自然过渡，并成为一个段落的主题句。 例：
The Influence of Advertising on Consumers
Advertisements are so pervasive nowadays that they almost guide our consuming behavior. People are more likely to buy a product which sounds and looks familiar to them. This is no doubt an advantage of ads; otherwise we’ll feel a loss in a supermarket hesitating to buy even a small article. Ads save our time and lessen anxiety in this respect. In a word, advertising plays a very important role in conducting our consuming behavior.
However, this advantage may be seen from the opposite angel as a disadvantage, like the two sides of the same coin. Ads are so persuasive that quite probably they can mislead consumers. Ads shape our consuming conception, encroaching into our private field of judging by ourselves. This has been valued as a mark of unique personal style, but now we are gradually losing it.
As a consumer, I love ads just as I hate them. Yet I don’t know how to deal with my contradictory feeling, since an individual consumer is almost defenseless in front of overwhelming ads.
在这篇文章里，第一段的中心内容就是结尾句：广告在指导我们的消费行为中扮演着非常重要的地位。这句结尾句使文章向第二段自然过渡， 第二段则从另一角度分析广告对我们消费理念的误导作用。考生应该注意并不是每一个段落都有结尾句。如果每个段落都按部就班地先写上主题句、扩展句，再不管是否必要，都写出一句结尾句，就会使文章显得呆板，缺乏生气。上面文章的第二段就没有总结全段内容的结尾句。 二、6种展开段落的方法
合理的发展方法能把中心思想和材料有机地组织起来，让读者读起来感觉自然、条理性强。常见的段落展开的方法有列举法、举例法、比较法与对照法、因果法、定义法和分类法等。
1. 列举法
在展开段落的时候，可以用列举的方法，列举主要的细节来展开段落，指出主题句的组成部分和具体内容，进一步说明主题句。用列举法展开段落，能增强文章的说服力，使文章显得条理清楚。 例如：
People welcome private schools for many good reasons. First of all, those people are willing to send their only child to better schools even if it costs more. And having more money than the government-funded public schools, those private schools can attract better teachers. They can also offer better environments, including superior living facilities and more advance teaching equipment.
在这段文字里，主题句是第一句，说明人们选择私立学校有很多好的原因。接着作者
用了第2、3、4句这三个一级扩展句来列举私立学校好的具体表现形式。
列举法是展开段落最常用的一种方法。在列提纲的时候，可以先根据文章的要求写出主题句，然后根据具体规定的范围想一想可以列举哪些方面的内容来进行说理。
比如，如果提纲是“社会实践的好处”，就可以先列出主题句和一级扩展句，然后再进行整理和充实：
主题句：There is no doubt that social practice has many advantages. 一级扩展句：
1） The students can apply what they have learned in class to practical work, which will make
them know themselves more clearly.
2）Some social practice can bring you some profit and it can make you more independent of your
parents.
3）Social practice can offer the students a chance to contact the society and get some idea of
society.
扩展句的列举顺序一般是按照各扩展句的重要性，从较次要到最重要，从小的方面到大的方面排列。上面三个扩展句可以这样排列：
Firstly, social practice can offer the students a chance to contact the society and get some idea of society. Secondly, the students can apply what they have learned in class to practical work, which will make them know themselves more clearly. Thirdly, some social practice can bring you some profit and it can make you more independent of your parents. 此外，扩展句的列举顺序还可以按照时间先后或空间顺序排列。
列举中常用的衔接词（组）有：
first most important of all next firstly moreover thirdly first of all besides fourthly to begin with secondly last
to start with second in addition first and foremost then finally in the first place furthermore lastly 2. 举例法
列举事实或举出实例，用以说明中心思想或论证某种观点，这种方法称为举例法。列举法是列举主题句的几个方面来充实主题句。举例法则是以具体的实例来充实主题句。在对主题句的内容具体表现在哪几个方面还不是非常了解的时候，用举例子的方法来扩充主题句是再好不过的了。举例法简单易行，具有较强的说服力和感染力。 例如：
Communicating with other people by telephone is very convenient, especially when you have something urgent. For example, if one of your family members is seriously ill at night, and you don’t know how to deal with it and where to find a doctor, what can you do? A telephone is the answer. Dial 120 and you will get services from the hospital very soon.
在这段话里，第一句是主题句，后面的扩展句是通过举例子来说明主题句的。用来为一级扩展句提供信息的二级扩展句通常以举例子的形式出现的。用举例子的方法来展开段落使文章更生动，更有说服力。
举例中常用的衔接词（组）有：
for example for instance
take…for example a case in point is..
this can be illustrated by as an illustration another example is… such as… like…
3. 比较法与对照法
通过指出事物之间的相似或共同之处来展开段落的方法就是比较法。在论述的主题不太容易说明或比较抽象时，应将要说明的主题与读者比较了解，并与它有相同之处的事物放在一起进行比较，指出它们之间的共同点，就能生动形象地阐明主题的内容及性质。 如：
Learning English is like building a house. Laying a solid foundation is the first and most important step. In other words, you should read and speak English every day. Memorizing new words and phrases is also helpful. Like building a house, learning English takes some time. So don’t be impatient. Remember, Rome wasn’t built in a day.
这段文字用合理的比较，将学英语和盖房子相比较，以盖房子需要打好坚实的基础作比较，来阐明学英语同样需要坚实的基础。盖房子需要时间，学英语同样也不是一蹴而就的，所以英语学习者要有耐心，最后用一句谚语：冰冻三尺非一日之寒，来结束该段落。用这种方法来阐明主题，使文章浅显易懂，深入浅出，容易让读者理解。
比较中常用的衔接词（组）有：
at the same time similar to accordingly both show a degree of similarity similarly (somewhat/very much) like and so… (exactly/almost) the same as and…too
in the same way in a like manner 对照法是将两事物进行对照，通过辨别其差异而指出各自的特征和本质。主题句指出事物之间的不同之处，扩展句进行详细说明。 例如：
The growth of video viewers has meant a decline in cinema audience. The attraction of cinema cannot compete with that of watching a video at home. People find it much cheaper and more comfortable to hire a video film to watch at home than to go out to the cinema. One or two yuan for a video film is nothing compared with the cost of cinema tickets and bus fares. Besides, video offers people the flexibility that cinema cannot provide. People are no longer limited to particular time and places, and they are able to watch a video film whenever and wherever they like.
本文把录像与电影作比较，从价格和灵活性两方面进行了对照，谁优谁劣，读者一看便知。
对比中常用的衔接词（组）有：
however but
yet nevertheless nonetheless conversely whereas though
on the one hand on the other hand on the contrary by contrast with/to in contrast even though instead of unlike