句子构成的成分共分为九种：主语，谓语，宾语，表语，定语，状语，补语，同位语和插入语。
一、主语：句子的核心主体，通常位于谓语动词之前，表明一个句子是谁或何种情况所发出执行或是承受的。在雅思写作中常做主语的有名词、代词、主语从句、V-ing 、To do五种。
1名词：Computers are now being widely used in almost all fields.
2代词：We are now living in an information-explosion era.
3主语从句：Whether sports stars should earn a high salary is still discussed heatedly.
4V-ing: Surfing the Internet offers a new way for people to relax themselves.
5To do: To protect the environment is everybody’s business.
二、谓语：描述或阐述主语的情况，由动词来充当，常位于主语之后。
1表状态用系动词：As I see it， movie stars’ earning a high salary is unfair and unjustified.
2表动作用及物或不及物动词：The Internet has revolutionized people’s way of life. Taste differs.
3表拥有：人或物时用：have has 无生命的东西：there be
People have different views on this question.
There is no absolute agreement on this question.
4情态动词＋动词原形：
In this way， teachers can never be replaced by computers.
三、宾语：及物动词或介词所指向的对象。在雅思写作中常做宾语的有名词、宾语从句、复合结构、V-ing 、To do五种。
1、名词作宾语：International tourism promotes the economic development.
2、宾语从句作宾语：Some people hold that air travel should be restricted.
3、复合结构：The advanced medical technology has made it possible for people to live longer than ever possible before.
4、V-ing: Nobody can avoid being influenced by media.
5、To do: Some people want to work for a big company while others choose to work for a small one. | 
