Natural resources are very limited．They will be exhausted in the near future．It is not true．But it becomes a major concern around the world．This is a widely accepted fact．
这段文字用简单句表达，它们之间内在的逻辑关系含糊不清，意思支离破碎。如果使用连接词，将单句与其前后合并，形成主次关系，就把一个比较复杂的内容和关系表达得层次清楚、结构严谨。例如：
It is a widely accepted fact that there is a major concern around the world for the exhaustion of limited natural resources in the near future，though it is unlikely to be true．
再如：
The Mississippi River is one of the longest rivers in the world，and in spring time it often overflows its banks，and the lives of many people are endangered．
此句用and把三个分句一贯到底，既乏味又可笑。如果使用了关系代词which，语义就会更连贯，语言也会更流畅：
The Mississippi River，which is one of the longest rivers in the world，often overflows its banks in the spring time，endangering the lives of many people．
三、长短句交插
长句和短句是就句子的字数多少、形体长短而言的。长句和短句各有其优点和缺点。长句，因为使用的定语、状语较多，限制了概念的外延，增大了概念的内涵，所以比较精确、严密，但使用起来不够活泼简便。短句，由于字数少，直截了当，一般比较简洁、明快、有力，但不利于表达复杂的语义内容。在具体语言活动中，最好长短句交替使用。这既体现了节奏上的要求，也是意义上的需要。例如：
（1）We can imagine the beautiful surroundings．（2）There are many trees along the streets．（3）There is a clean river in the city．（4） There are many fishes in the river．（5）There are willow trees on the one side．（6）There are some pieces of grassland on the other side．（7）There are many flowers on them．
文中七个句子都是简单句，句型结构单一，而且句子长短同一，都在七、八词左右，十分单调。下面是修改后的段落：
（1）Just imagine the beautiful surroundings if we make our cities greener．（2）Green trees line the streets．（3）A clean river winds through the city，in which a lot of fishes abound．（4）On the one side stand rows of willow trees．（5）On the other side lies a stretch of grassland sprinkled with many yellow and red flowers．
改写后的这段文字，有长句（1）、（3）、（5），也有短句（2）和（4），一长一短，抑扬顿挫的节奏感就出来了。不仅句子长短交插，而且句型结构变化也很大，使文章流畅自然，生动活泼。
四、利用倒装结构
英语的基本句型是S＋V＋O，如果偶尔打破常规，改变某一成分的位置，不仅可以丰富句型，而且能强调、突出被倒装的部分，收到意想不到的表达效果。例如：
1）In no other place in the world can one find such enthusiasm for applying for hosting the 2008 Olympic Games．
2）Faith in the Chinese economic reforms the majority of people will never lose．
总之，英语的句式是多种多样的，只要从要表达的内容出发合理选用，文章的句式就会富于变化。同时，在学习写作的过程中，学生应不断练习构造各种各样句式，以提高语言表达能力。