A. before用法 问题： before的用法有哪些
prep. 在......以前，强调时间
He came to see me the day before yesterday. 他前天来看我了。
2. prep. 在......前面，当着......的面，向......，强调地点
She has to appear before the court. 她必须出庭受审。
3. prep. 在......之前，先于，强调次序
Those with babies can get on the bus before others. 带小孩的人可以先上汽车。
4. prep. 与其......（宁愿）
I'd shoot myself before I apologized to him! 我宁死也不向他道歉!
5. adv. 以前，强调时间
We've seen that film before. 我们以前看过那场电影。
6. adv. 在前面，向前，强调位置
Don't run before and after. 别跑前跑后。
7. conj. 在......前，强调时间
before的含义比较灵活，实际翻译时应结合具体情况机动处理。
趁......
You should do it before it is too late. 趁现在还不算太晚，你应该赶快做它。
2. 尚未来得及
Before she could move, she heard a loud noise, which grew to a terrible roar. 她还没有来得及动弹，就听见有很响的声音，接着就成了可怕的隆隆轰鸣声。
Before they reached the house, a new great wave came, sweeping down trees, and sweeping them down too. 他们还没到屋子，又一个巨浪打来，冲倒了树，也冲倒了他们。
3. 要......先......
You should be a pupil before you become a teacher. 要当老师，先作学生。
二、掌握热点句型用法
It was not long before...（过去）没过多久就......
It was not long before he returned to Beijing. 不久他就回到北京。
需要特别注意，该句型可以进行创新，可将否定句改为肯定句（It was long before...过了很久才......）或将一般过去时改为一般将来时（It will not be long before...要不了多久就......；It will be long before...要过很久才......）。before在这些句型中均引导时间状语从句， long这个抽象的时间也可改为years, weeks, days等具体表时间的词。
It was long before he married Wei Fang. 过了很久他才娶魏芳。
It will be long before he goes abroad. 要过很久他才出国。
Will it be years before he goes to school? 要过好几年他才能上学吗？
since的用法：译作“自从…以来”
(1)接时间点：如 I have stayed in that country since 1995.要求：谓v.用现在完成时,而且须是延续性动词.
(2)接一段时间 + ago：如 They have lived in that house since two years ago.
要求：谓v.用现在完成时,而且须是延续性动词.
(3)接时间状语从句：如 I have loved her since I met her last time./ Lily has stayed at home since she left school.
要求：主句的谓v.用现在完成时,而且须是延续性动词；从句的谓v.用一般过去时,而且须是终止性动词.
(4)用于句型“It’s / It has been + 一段时间 + since + 时间状语从句”中,译作“自从…以来,已经…(时间)了”.
如 It’s / has been three months since he moved to this city.
要求：主句的谓v.用一般现在时或现在完成时；从句的谓v.用一般过去时,而且须是终止性动词.
(5)用于句型“一段时间 + has passed since + 时间状语从句”中,译作“自从…以来,…
(时间)已经过去了”.
如上个例句还可写成：Three months has passed since he moved to this city
.要求：主句的谓v.用现在完成时,而且动词必须是has passed；从句的谓v.用一般过去时,而且须是终止性动词.
(6)注：当since用于否定句时,主句的谓v.可以是终止性动词.
如 He hasn’t seen the film since last month.
(7)相关词组：“从那时起”：ever since、since then、from then on.
注：ever since作为一个词组,放句尾可单独使用.
如I have given up smoking ever since.另外,还可在since后接句子.since前加ever,只是加重语气而已.
如 I have given up smoking ever since I caught a bad cough.
(8) since还可引导原因状语从句,译作“由于；因为”,相当于because.
如 Since he was lazy,he didn’t finish his homework.
that 用法
pron.
1.那;那个,那人,那事,那东西
That's my English teacher over there.
那边是我的英文老师.
2.(已被提到的)那个,那人,那事,那东西
Who told her that?
那是谁告诉她那件事的?
3.前者
4.(用作关系代词的先行词)那,那个
What is that which you have just stuffed into the plastic cup?
你刚才塞在塑料杯里的是什么东西?
5.(代替句中名词,避免重复)
The output of steel this year has increased by 20% compared with that in 1992.
今年钢产量比一九九二年增长了百分之二十.
6.(用作关系代词,引导关系从句)
a.
1.那,那个
That book isn't mine.
那本书不是我的.
ad.
1.【口】那样,那么
Is the problem that easy?
问题有那么简单吗?
conj.
1.(引导名词从句)
He expressed the hope that we would keep in touch with his firm.
他表示希望我们与他的公司保持联系.
My idea is that we should act on his suggestion.
我的意见是我们应当按照他的建议去办.
That she is still alive is a relief.
她还活着,这是令人感到宽慰的.
2.(引导状语从句,表示原因或理由)因为,由于
We are glad that we have accomplished another arous task.
我们都感到高兴因为又完成了一项艰巨的任务.
3.(引导状语从句,表示目的或结果)为了,以至于
He is working hard that he can catch up with the class.
他努力用功,以便赶上班上同学.
4.(引导表示愿望,感叹的从句,主句常省略)
That I could stay at home today!
今天要是我能呆在家里多好呀!
after
1介词:
(a) Please come to my house after dinner.晚饭后
(b) He ran after the bus.追赶
(c) His mother waited for him night after night.（一个）接着（一个）
(d) It's sad to fail after all that work.由于
(e) They are still friends after all their differences.
2 副词:
(a) three hours after; (b) departed shortly after; (c) after all I don't really know him.终究
(d) He told me afterwards that he had not enjoyed the film.后来
3连词:
(a) I saw them after I arrived.后来
(b) They arrived soon after.后来
(c) tomorrow,or the day after...
4 名词:
(a) afternoon午后; (b) afterthought事后的想法; (c) aftermath后果
一 .when 用作副词.
1.用作疑问副词,引导特殊疑问句.例如：
When will you come to see me?你什么时候要来看我?
When are they going to visit the Great Wall?他们打算什么时候去游览长城?
2.用作连接副词,通常用来引导主语从句、表语从句、同位语从句、宾语从句及起名词作用的“ when ＋动词不定式”结构.例如：
When he comes is not known.他何时来还不知道.
The morning is when I am busiest.早上是我最忙的时候.
I have no idea when the game will begin.我不知道比赛何时开始.
I don't know when the plane takes off.我不知道飞机何时起飞.
I don't know when to leave for London.我不知道该在何时动身去伦敦.
3.用作关系副词,引导限定性定语从句和非限定性定语从句.例如：
Do you still remember the days when we stayed in America?你还记得我们呆在美国的那些日子吗?
The day will come soon when the Chinese astronauts will go to the moon.中国宇航员登上月球的那一天很快就要到来了.
It happened ten years ago,when I was a child.事情发生在十年前,当时我还是个小孩子.
We will go to the countryside at the beginning of June,when the summer harvest will start.我们将在六月初下乡,那时夏收就要开始了.
二 .when 用作连词.
1.用作从属连词,意为“当……的时候”,引导时间状语从句.例如：
They learned a lot from the peasants when they stayed in the village.
他们住在那个村子时,从农民那里学到了许多东西.
It was snowing when he arrived at the station.他到达车站时,天正下着雪.
注意：如果 when 引导的从句中的主语和主句中的主语一致,且从句中的谓语动词是“ be ＋分词”或从句主语是 it ,则 be 动词及其主语常可省略.例如：
When （ he was ） asked why he was late,he made no answer.当被问到他为什么迟到时,他避而不答.
I'll tell him about it when （ it is ） possible.在可能的时候,我会把那件事告诉他的.
2.用作从属连词,意为“一……就……”,引导时间状语从句.例如：
We will stand up when the teacher comes into the classroom.老师一进教室我们就起立.
Fire the rockets when I give the signal.我一发信号,你就点燃火箭.
3.用作从属连词,意为“还没 / 刚刚……就”,引导时间状语从句.例如：
I had hardly opened the door when he came in.我刚一开门,他就进来了.
I had not been reading for half an hour when I heard someone call my name.我刚刚看了半个小时的书,就听到有人叫我的名字.
4.用作从属连词,意为“倘若,如果”,表示条件.例如：
He will be likely to recover when he is operated on.如果动手术,他有可能康复.
Turn off the switch when anything goes wrong with the machine.如果机器发生故障,就把电源关上.
5.用作从属连词,意为“既然,尽管”,表示让步.例如：
Why use metal when you can use plastic?既然能用塑料,为什么用金属呢?
They kept trying when they knew it was hopeless.尽管他们知道那件事没有希望,可是他们还在不断地努力.
6.用作并列连词,意为“在那时,届时”,表示时间.这时主句中可以用过去进行时,过去完成时或“ was/were about to do sth.”结构.例如：
Last night I was about to go to bed when the phone rang.昨天晚上我正要上床睡觉时,电话铃响了.
I was cooking in the kitchen when someone knocked at the door.我正在厨房做饭,这时有人敲门.
He had just finished the book when supper was served.我刚刚读完这本书,这时晚饭就端上来了.
7.用作并列连词,意为“虽然、然而、可是”,表示转折.例如：
He usually walks to work when he might take a bus.虽然他可以坐公共汽车上班,但他却常常步行上班.
I had only twenty dollars when I needed thirty to buy the dictionary.
我需要 30 美元买那本字典,可是我只有 20 美元.
8.用作并列连词,意为“而、却”,表示对比.例如：
How can he say that everything is fine when it's obvious that it is not?他怎能说一切都好呢?情况显然不是那样.
三 .when 用作代词.
when 作为代词常常位于介词之后,意为“那时,什么时候”.例如：
We came back on Tuesday,since when we have been working in the repair shop.我们星期二回来,从那时起就一直在修配车间工作.
Since when have you been studying Japanese?你是从何时起一直学习日语的?
另外,when 还可用作名词,前面常常用定冠词 the .the when 表示事件发生的时间,常常与 the where,the how 并列使用.例如：
He told the police the when and the how of the accident.他告诉警察事故发生的时间及发生的原委.