二、句子按其结构可以分为简单句、并列句和复合句。

1. 简单句：The Simple Sentence由一个主语(或并列主语)和一个谓语(或并列谓语)构成的句子。
　　e.g. I get up at six thirty in the morning.
　　My mother and I often go shopping.

2. 并列句：The Compound Sentence 由并列词and, so, but, or等)把两个或两个以上的简单句连在一起而构成的句子。要掌握并列句的构成及用法。
　　e.g. I help him and he helps me. 我帮他，他帮我。
　　This is our first lesson, so I don't know all your names.
　　这是我们的第一节课，所以我不认识你们。
　　She likes bread and milk , but she doesn't like eggs at all.
　　她喜欢吃面包和牛奶，但她一点儿也不喜欢吃鸡蛋。

3. 复合句：The Complex Sentence 由一个主句和一个或一个以上的从句构成的句子。
　　e.g. If you are ill, you must see the doctor.
　　如果你病了，一定要去看医生。(状语从句)
　　I hope he's better tomorrow.
　　我希望他明天身体更好一些。(宾语从句)
　　熟练掌握宾语从句的语序及关联词that, if / whether, what, who, which, whose, when, what time, where, how 等的用法，以及宾语从句的时态。
　　在复合句中作主句的宾语，叫宾语从句。
　　注意：宾语从句的语序必须是陈述句语序。
　　e.g. I asked him if he was a student.
　　宾语从句的时态呼应是：主句的时态是一般现在时，从句可以是任何一个时态。
　　如果主句的时态是一般过去时，从句必须是过去时态的一种形式。
　　当表示事实、真理、自然现象时必须用一般现在时。
　　e.g. The teacher told us that the earth goes around the sun.
　　老师告诉我们地球围绕太阳转。
　　请注意防止出现以下错误：
　　A. They said that they'll leave if Peter stays.
　　时态错误，应改为：They said that they would leave if Peter stayed.
　　B. He asked why were you late for school.
　　语序错误，应改为：He asked why you were late for school .
　　C. Her brother asked me whose book this was?
　　标点错误，问号应该改为句号。
　　熟练掌握由when, before, after, as soon as, until, because, than, if, so …that等词引导的时间、原因，比较，条件、结果状语从句。
　　在复合句中修饰主句中的动词，形容词或副词等的从句叫作状语从句。
　　时间状语从句：
　　When she reached home , she had a short rest.
　　当她到家时，她休息了一会儿。
　　Judy had finished writing the book before she went to Queensland. 朱娣在去昆士兰之前已经写完了那本书。
　　I went to bed after I finished my article. 我写完文章之后才上床。
　　As soon as the bell rang the students, stopped talking to each other. 铃声一响，学生们就停止了谈话。
　　We won't leave until the head teacher comes back. 班主任回来我们才会离开。
　　原因状语从句：
　　The children went to the farm, because the farmers needed some help. 孩子们去农场是因为农民们需要帮忙。
　　比较状语从句：Jim is older than Lucy is. 吉姆比露西大。
　　条件状语从句：
　　If it rains tomorrow , we won't hold a sports meeting on the sports ground. 如果明天下雨，我们就不在运动场上开运动会了。
　　结果状语从句：
　　The box is so heavy that I can't lift it. 这个箱子太沉以致于我无法抬起来。
　　目的状语从句：
　　The headmaster spoke loudly so that all the students could hear what he said. 校长高声讲话为的是全体学生能够听到他所讲的话。
　　让步状语从句：
　　Although he is young , he knows a lot of things. 虽然他年龄小，但却认识许多事情。
　　状语从句的时态要与主句时态相互呼应。但要注意以as soon as, when, until等引导的时间状语从句表示将来的动作时，从句要用一般现在时表示将来。
　　e.g. He will write to me as soon as he gets to America. 他一到美国就给我写信。
　　When I see him , I will tell him this good news. 当我见到他时，我将告诉他这个好消息。
　　We won't leave until we finish our homework. 直到完成作业我们才会离开。
　　以if引导的条件状语从句假设的是将来的动作，主句用一般将来时，从句用一般现在时。
　　e.g. He will come to see me if he has time. 如果条件状语从句放在宾语从句中，时态则依照宾语从句的要求而变。
　　e.g. My mother said she would buy me a book if I studied hard. 我母亲说如果我努力学习，她要给我买一本书。
　　以because引导的原因状语从句不可能和so一起连用。
　　e.g. He didn't come to school yesterday because he was ill. 他昨天没来学校，因为他生病了。