2. Since everybody is here, let’s begin our meeting.

　既然大家都来了, 让我们开始开会吧.

　要点: 由连词BECause, since, as引导, 也可由for, now that 等词引导

1.I didn’t go to school yesterday BECause I was ill.

　我昨天没去上学，因为我生病了。

4.You will be late unless you leave immediately.

　如果你不马上走,你将会迟到的.(=If you don’t leave immediately, you will be late.)

　难点提示：用条件状语从句时要注意时态的正确使用,当主句是将来时的时候,从句要用一般现在时.

　He will not leave if it isn’t fine tomorrow.

　一般将来时， 一般现在时

　They are going to have a picnic if it doesn’t rain next week.

　一般将来时, 一般现在时 考点

3.I will go to the party unless he goes there too.

　我不会去参加聚会的, 除非他也去.(如果他不去,我也不去.)

2.You will get good grades if you study hard.

　如果你努力学习,就会取得好成绩.

　要点： 表示状语从句由连词if, unless (=if not) 引导。

1.If it doesn’t rain tomorrow, we will go hiking.

　如果明天不下雨, 我们就去远足.

2. It is +before…(。。。才)

　It was a long time before I went to sleep again.

　过了很长时间我才睡着。

　It was an hour before(＝until) the police arrived.

　过了一个小时，警察才来。

1. It is since从。。。以来多长时间了(因为since +从句或名词，表示一段时间)

　It is five years since we met last time.从我们上次见面已经五年了。

2、 强调两个动作同时进行，并表示对比时

　有时这三个连词可以互换，有时不可以。

　It was raining hard when (as) I got there.

　我到那里时，正在下大雨。 ( 动作同时发生，when可换为as, 但不能换为while，因为get是点动词.)

　When I had read the article, he called me.

　我看完这篇文章之后，她给我打了电话。( 从句动作发生在主句之前，注意时态表达，只能用when )

　When I got to the cinema, the film had begun.

　(当)我到了电影院时，电影已经开演了。(从句的动作发生在主句之后，只能用when,并要注意时态)

　He was about to leave, when the telephone rang.

　他正要离开，忽然电话响了。( 此时不能放在句首。主句动词一般表达 “正在” “即将”.

　while, as不能代替 ) 考点

　She thought I was talking about her daughter, while, in fact, I was talking about my daughter.

　他以为我在谈她女儿，然而，实际上在谈论我女儿。(表转折，对比，when, as都不能代替它) 考点

　lWhile the alien was buying a souvenir, the girl called the police.

　外星人买纪念品时，那女孩给警察打了电话。(表示主句，从句的动作同时发生，while后引导的状语从句的动词必须是延续动词不能是点动词，因为它表示较长时间)考点

　Mother was worried BECause little Alice was ill, especially as (when/ while) father was away.

　妈妈担心，因为小爱丽丝病了，特别是他父亲不在家的时候。(此时as ,when, while可通用)

　知识扩展

1、用于时间较长时