2022年初中英语从句知识点总结归纳3

1、精选学习资料 - - - 欢迎下载精品学习资料宾语从句一 定义：宾语从句为指在一个句子中充当宾语的句子如： he said that he wanted to be a teacher when he grew up.二宾语从句有三种类型：1由从属连词 that 引导的宾语从句表示陈述意义,连词that 常可被省略；例如： i hope that they will have fun. mary said that she felt sleepy.cant you see that im a bird.留意： （1）当主句的谓语动词为think、believe 等时,宾语从句尽管要表示否定意义

2、,却不用否定形式, 而将 think 等动词变为否定形式； 如：i dont think hewill come.我认为他不会来；（2）两个表示陈述意义的宾语从句并列时,有时省去第一个从句的连词that,但其次个从句的连词that 一般不行以省略；如：he told me thatthey could not decide what to do and that they asked myadvice.2.由从属连词 if 或 whether引导的宾语从句表示 “为否（有,能,已经）”等一般疑问句的含义；例如： i wonder whether if he lives here.3.由连接代词

3、 who、whom、whose、what、which 和连接副词 when、where、how、why 等引导的宾语从句表示“谁,谁的,什么,哪（个,些）,何时,何地,怎样,为什么”等等特殊疑问句的意义； 除了连接词及被修饰的词提前以外, 宾语从句用陈述句语序；例如： to masked who could give the message to her mother.do you know what he said just now. i wondered how old his brother was.三.宾语从句的时态呼应：“主现就从任,主过就从过,客观真理一般现”1当主句为现在时或将来

4、时的时候,宾语从句可以用所需要的任何时态；2主句为过去时,宾语从句一般只能用过去时的某种形式；当从句表达的为客观事实或一般真理时,宾语从句仍旧用现在时态；3情态动词 must 一般不用于过去时, 但却可以用于主句为过去时的宾语从句中；四.宾语从句的语序1宾语从句的连接词后加陈述语序（主语在前,谓语在后）如： i want to know if he can come tomorrow2当连接词本身又为宾语从句的主语时,后面直接加谓语动词如： she asked me who had helped him状语从句英语中 、修饰动词.形容词.副词等的句子成分叫状语；状语的功用：状语说明地点.时间.

5、缘由.目的.结果.条件.方向.程度.方精选学习资料 - - - 欢迎下载精品学习资料式和相伴状况等, 依据状语的功能状语从句可分为：时间状语从句. 缘由状语从句.目的状语从句.结果状语从句.条件状语从句；一时间状语从句：在一个句子中作时间状语的句子；时间状语的连接词： when（当时候）while（当时候） as（当时候） after（在以后）before（在以前）as soon a（s 一就）since（自从到现在）till /until （直到才）by the time（到为止）照旧为连接词后加陈述语序；1.when当的时候（一般情形下：主将从现）i will become a teach

6、er when i grow up2.while当时he visited a lot of places while he was traveling.3.as在的同时；一边一边he smiled as he stood up.4.after在之后he left the classroom after he had finished his homework the other day.5.before在之前mr. brown had worked in a bank for a year before he came here.6.as soon as一就一般情形下：主将从现 we bega

7、n to work as soon as we got there.i will write to you as soon as i get home.7.since自以来 到现在表示自过去的一个起点时间到目前说话时间 为止的一段连续时间；主句一般用现在完成时,从句用一般过去时；mr green has taught in that school since he came to china three years ago 仍 . 可以用作介词,本句从句仍可以用短语：since three yearsago自8till /until直到三年前以来 表示； 都可以作连词,连接时间状语,也可以作介

8、词,与其它词构成介词短语,在句中作状语；they walked till /until it was dark.xiao ming didnt leave home till / until his father came .back9.by the time到为止所在句子的主句应用现在或过去完成时 by the time he gets there 、 his father has already gone.by the time i got to school、 the class had already began.用法辨析： 1.when、 while 和 as的区分when引导的从句

9、的谓语动词可以为连续性的动词,又可以为瞬时动词；并且when 有时表示“就在那时” ；例如： when she came in、 i stopped eating.她进来时,我在吃饭； 瞬时动词来了；when i lived in the countryside、 i used to carry some water for him.当的住在农村时,我经常为他担水； （连续性的动词）we were about to leave when he came in.我们就要离开,就在那时他进while引导的从句的谓语动作必需为连续性的,并强调主句和从句的动作同时精选学习资料 - - - 欢迎下载精品

10、学习资料发生（或者相对应） ；并且 while 有时仍可以表示对比；例如：while my wife was reading the newspaper、 i was watching tv .i like playing football while you like playing basketball. 我喜爱踢足球,而你喜爱打篮球；（对比）as表示“一边一边”,as引导的动作为连续性的动作,一般用于主句和从句动作同时发生； as也可以强调“一先一后；例如： we always sing as we walk.我们总为边走边唱； （as表示 “一边一边”）as we was going

11、out、 it began to snow.当我们出门时,开头下雪了； （as强调句中两个动作紧接着先后发生,而不强调开头下雪的特定时间）as when while都表示主.从句动作同时发生,三者差异如下：as表示“一边；一边的意思when1.仍可以表示从句动词的动作在主几句动词的动作之前或之后发生；2.whenand then; at that moment 正3.常用于常见搭配中while1. 用于时间较长时在那个时候 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,有时不行以；lt was raining hard when as i got there.我到那里时,正在

12、下大雨； 动作同时发生, when可换为 as、 但不能换为 while,由于 get为点动词 .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,留意时态表达,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、并要留意时态 he was about to leave、 when the telephone rang.他刚要离开,突然电话响了；此时不能放在句首；主句动

13、词一般表达 “正在” “即将” .while、 as 不能代替she thought i was talking about her daughter、 while、 in fact、 i was talkingabout 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 while 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需为连续动词不能为点动

14、词,由于它表示较长时间mother wasworried becauselittle alice was ill、especially as when/ whilefatherwas away.妈妈担忧,由于小爱丽丝病了, 特殊为他父亲不在家的时候； 此时 as 、when、while精选学习资料 - - - 欢迎下载精品学习资料可通用 2. 由 till 或 until 引导的时间状语从句；till 和 until 一般情形下两者可以互换,但为在强调句型中多用until ；并且要留意的为：假如主句中的谓语动词为瞬时动词时, 必需用否定形式； 假如主句中的谓语动词为连续性动词时,用确定或否定形

15、式都可以,但表达的意思不同；例如：i worked until he came back我. 工作到他回来为止；i didnt work until he came back.他回来我这才开头工作；3. 由 since引导的时间状语从句；since引导的从句的谓语动词可以为连续性的动词,又可以为瞬时动词；一般情形下,从句谓语动词用一般过去时,而主句的谓语动词用现在完成时,表述为：现在完成时 +since+一般过去时；但在it is 时间 since从句的句型中,主句多用一般现在时；例如：it is five months since our boss was in beijing我.学问扩展1

16、. it issince从.以来多长时间了it is five years since we met last time.2. it is+before；才； it was a long time before i went to sleep again.it was an hour before until the policearrived. 二.们老板离开北京有五个月了；缘由状语从句：在一个句子中作时间状语的句子；连接词：由连词 because、 since、 a引s 导、 也可由 for、 now that 等词引导1.i didnt go to school yesterday be

17、cause i was ill.2. since everybody is here、 lets begin ou既r m 然 e；e；ti；ng.3. as you are in poor health、 you should not stay up late. 既然；4.i asked her to stay to tea、 for i had something to tell her.用法辨析： because 、 since 、 as 、 fo辨r析1）because语势最强,用来说明人所不知的缘由,回答why 提出的问题；当缘由为显而易见的或已为人们所知,就用as 或since；i

18、 didnt go、 because i was afraid.since /as the weather is so bad、 we have to delay our journey.2）由 because引导的从句假如放在句末,且前面有逗号,就可以用 for 来代替；但假如不为说明直接缘由,而为多种情形加以推断,就只能用for；he is absent today、 because / for he isill. he must be ill、 for he is absent today.三.条件状语从句连接词： if 假如、 unless =if not假如不.除非 让步1 .if

19、it doesnt rain tomorrow、 we go wh ili lking.2 .i will go to the party unless he goes there too.3 .you will be late unless you leaveimmediately.=if you dont leave immediately、 you will be late.条件状语从句：主将从现.he will not leave if it isnt fine tomorrow.精选学习资料 - - - 欢迎下载精品学习资料四.目的.结果状语从句目的状语从句为指在一个句子中充当目的状

20、语的句子；结果状语从句为指在一个句子中充当结果状语的句子目的状语从句连接词so that、 sothat 、 in order that 引导；结果状语从句连接词sothat、 suchthat、 so much/manythat引导；1.sothat如此以至于he always studied so hard that he made great progress.2.so that以至于 、 以便于i ll run slowly so that you can catch up with me.目的i opened the window so that fresh air might co

21、me in.目的3.suchthat如此以至it s such nice weather that all of us want to go to the park.4.in order that=so that为了we shall let you know the details soon in order that you can/may make yourarrangements.5.比较： so 和 such其规律由 so 与 such 的不同词性打算； such 为形容词,修饰名词或名词词组,so 为副词,只能修饰形容词或副词；so 仍可与表示数量的形容词many、few、 much

22、、 little 连用,形成固定搭配；so nice a flowersuch a nice flowerso many / few flowerssuch nice flowersso many peoplesuch a lot of people（ so many 已成固定搭配, a lot of虽相当于many,但 a lot of为名词性的,只能用 such搭配；）难 点so+形容词或副词so+形+aan+单数可数名词 so +many /few+复数可数名词so +much/ little+不行数名词sothat与 suchthat 皆可引导目的地状语从句和结果状语从句；the bo

23、y is so young that he can t go to school.he is such a young boy that he can t go to schoolso +adj/adv.+ tha, tsuch +n.+ that 以上两种句型都表示结果so 为副词、后接形容词,副词原型,可数名词前有many、 few；不行数名词前有 much、 little 修饰时,应采纳句型： so many few、 much、 little +n.such 为形容词 、 后只能接名词；这名词既可以地可数的,也可以为不行数的；假如这名词为可数的、就必需在名词前加不定冠词aan. 常见的

24、形式为 :such a beautifulgarden、 suchnicepeople.五.让步状语从句让步状语从句为指在句子中作让步的状语的句子连接词：though、 although.,whether or not难点： though、 although 当“虽然”讲 、 都不能和 but 连用. although/thoughbut的格式为不对的 .但为他们都可以同yet still连用. 所以 thoughtalthough精选学习资料 - - - 欢迎下载精品学习资料yetstill 的格式为正确的 .wrong: although he is rich but he is not

25、happy.right : although he is rich、 yet he is nothappy.虽然他很富有 、 然而他并不欢乐 .right : although we have grown up、 our parents treat us as childrenright : although we have grown up、 our parents still treat us aschildren.尽管我们已经长大了 、可为我们的父母仍把我们看作小孩 .although、 though 辨析although不能作并列连词, although不能作副词,放在词尾表示强调时要

26、用eventhough.1.even though i didnt under a word、 i kept smiling.尽管典型例题1）she is young、 she knows quite a lot.a. whenb. howeverc. althoughd. unless2)ever if、 even though.即使well make a trip even though the weather is bad.3) whetheror not不管都whether you believe it or not、 it is true.no matter 从句结构：no matt

27、er +特殊疑问词疑问词 +陈述语序 或特殊疑问词 +后缀 ever+陈述语序no matter what happened、 he would notmind. whatever happened、 he would notmind.替换： no matter what = whateverno matter who = whoeverno matter when = wheneverno matter where = whereverno matter which = whicheverno matter how = however留意： no matter 不能引导主语从句和宾语从句；（

28、错） no matter what you say is not useful now.（对） whatever you say is not useful now.你现在说什么也没用了；whatever you say为主语从句 （错） prisoners have to eat no matter what the y re given、（对） prisoners have to eat whatever the y定语从句re given.囚犯们只能给什么吃什么定语为指在句子中用来修饰名词.代词的成分定语从句为指在一个句子中作定语的句子,定语从句要放在所修饰的词后如： i have me

29、t the doctor who is in the no.1 hospital.定语从句的连接词：1.连接代词： who.which.whom.whose.that2.连接副词： when.where.why选用连接词的关键为看先行词定语从句所修饰的名词或代词 一.连接代词的选用：1.who指人,先行词为人 、在从句中做主语yesterday i helped an old man who lost his way.精选学习资料 - - - 欢迎下载精品学习资料2.whom指人,先行词为人 、在定语从句中充当宾语,常可省略；mr. liu is the person whom you tal

30、ked about on thebus.留意：关系代词 whom 在口语和非正式语体中常用who 代替,可省略；3.which指物,先行词为物 、在定语从句中做主语或者宾语,做宾语时可省略this is the pen which he bought yesterday.4.that指人时,相当于 who 或者 whom；指物时,相当于which；在定语从句中做主语或者宾语,做宾语时可省略；the number of the people that/who come to visit the city each year rises one million.where is the man t

31、hat/whom i saw this morning.5.whose 通常指人,也可指物,在定语从句中做定语、译成 .的he has a friend whose father is a doctor.指物时,常用以下结构来代替do you like the book whose cover is yellow. = do you like the book the color ofwhich is yellow.介词+连接代词引导的定语从句连接代词在定语从句中做介词宾语时、从句常由介词+连接代词引导the school that/which he once studied in is ve

32、ryfamous. the school in which he once studied is veryfamous.留意：1. 含有介词的动词短语一般不拆开使用,如：look for、 look after、 takecareof 等this is the watch which/that i am looking for.t this is the watch for which i am looking.f2. 如介词放在连接代词前,连接代词指人时用whom,不行用 who 或者 that；指物时用 which,不能用 that；连接代词为全部格时用whosethe man with

33、whom you talked is my friend.the plane in which we flew to canada is very comfortable. t3. “介词 +连接代词”前可有some、 any、 none、 both、 all、 neither、most、 each、 few 等代词或者数词he loved his parents deeply、 both of whom are very kind to him.in the basket there are quite many apples、 some of which have gone bad.the

34、re are forty students in our class in all、 most of whom are from bigcities二.连接副词的选用：1. when指时间,在定语从句中做时间状语i still remember the day when i first came to the school.2. where指地点,在定语从句中做地点状语shanghai is the city where i was born.3. why 指缘由,在定语从句中做缘由状语please tell me the reason why you missed the plane.留意：

35、关系副词引导的从句可以由“介词+关系代词”引导的从句替换the reason why/ for which he refused the invitation is not clear、from the year when/in which he was going to school he began to know what hewanted when he grew up.great changes have taken place in the city in which./where i was born.精选学习资料 - - - 欢迎下载精品学习资料三.判定关系代词和关系副词的方法

36、: 精确判定先行词在定语从句中的成分主.精选学习资料 - - - 欢迎下载精品学习资料谓.宾.定.状 例 1. is thisthe museumyou visited a few days ago.a. whereb. thatc. on whichd. the one例 2. is thisthe museumthe exhibition was held.a. whereb. thatc. on whichd. the one关系词的挑选依据在从句中所做的成分,先行词在从句中做主.定.宾语时,挑选关系代词who、 whom、 that、 which、 whose；先行词在从句中做状语时,

37、 应挑选关系副词 where 地点状语,when 时间状语,why 缘由状语 四.介词+连接词用法说明1）介词后面的关系词不能省略； 2）that 前不能有介词；3）某些在从句中充当时间, 地点或缘由状语的 介词+关系词 结构可以同关系副词 when 、where和 why 互换如：this is the house in which i lived two years ago. this is the house where i livedtwo years ago.do you remember the day on which you joined our club.do you rem

38、ember the daywhen you joined our club.this is the reason why he came late.this is the reason for which hecame late.五限制性定语从句和非限制性定语从句限制性定语从句举例：china is a country which has a long history.非限制性定语从句举例：his mother、 who loves him very much、 is strict with him.要留意区分以下几个句子的不同his brother who is now a doctor a

39、lways encourages him to go to college.他那当医生的哥哥常勉励他要考上高校；（他仍有其他的哥哥）his brother、 who is now a doctor、 always encourages him to go to college.他的哥哥为当医生的,常勉励他要考上高校；（他只有一个哥哥）关系代词 as和 which 引导的定语从句as和 which 引导非限制性定语从句,有相同之处也有不同之处；详细情形为：1as和 which 都可以在定语从句中做主语或者宾语,代表前面整个句子；(1) he married her、 as/which wasna

40、tural.(2) he was honest、 as/which we can see.2. as引导非限制性定语从句, 可放在主句之前, 或者主句之后, 甚至可以切割一个主句；which 引导的非限制性定语从句只能放在主句之后；另外, as有“ 正如,正像” 的意思as is known to all、 china is a developing country.he is from the south、 as we can see from hisaccent. john、 as you know、 is a famous writer.he has been to paris more

41、 than several times、 which i dont believe.留意：当主句和从句存在规律上的因果关系时,常用which精选学习资料 - - - 欢迎下载精品学习资料tom was always late for school、 which made his teacher angry.3. 当先行次受 such、 the same修饰时,常用 asi have never heard such a story as he tells.he is not such a fool as he looks.this is the same book as i lost last

42、 week.留意：当先行次由 the same修饰时,有时也用 that 引导定语从句, 但为和由 as 所引导的定语从句意思不同she wore the same dress that she wore at marys wedding.她穿着她在 mary 婚礼上穿过的一条裙子；she wore the same dress as her young sister wore.她穿着和她妹妹所穿的一样的裙子；以 the way为先行词的定语从句通常由in which、 that 引导,而且通常可以省略；the way in which/ that/./ he answered the que

43、stion was surprising.but 有时也可以做关系词引导定语从句there are very few but understand his idea. but= who dont 定语从句只能用 that 的几种情形1当先行词为 anything、 everything、 nothing something 除外、 few、 all、none、 little、some等代词时,或者为由every、 any、 all、 some、 no、 little、 few、much等修饰时 have you taken down everything that mr. li has sai

44、d.all that can be done has been done.there is little that i can do for you.留意：当先行词指人时,有时也可以用whoany man that/who has a sense of duty wont do such a thing.2. 当先行词被序数词修饰the first place that they visited in london was the big ben.3. 当先行词被形容词最高级修饰时this is the best film that i have seen.4. 当形容词被 the very、

45、 the only 修饰时this is the very good dictionary that i want to buy、当先行词指人时,有时也可以用whowang hua is the only person in our school who will attend the meetin？g5. 当先行词前面有 who、 which 等疑问代词时who is the man that is standing there.6. 当先行词既有人,也有动物或者物体时can you remember the scientist and his theory that we have lea

46、rned.同位语从句（一）一般来说,在主从复合句中,用作同位语的从句叫同位语从句；它通常跟 在某些名词之后, 用以说明或说明该名词表示的详细内容；可以跟同位语从句的名词通常有： advice、 decision、 fact、 hope、 idea、 information、 message、news、 promise、 proposal、 reply、 report、 suggestion、 wor （ d 消息） ,problem,question、 doubt、 thought等；they were delighted atthe news thattheir team had won.有

47、时同位语从句可以不紧跟在被说明的名词后面,而被别的词隔开；如：the thought came to him that tom might have returned the book.精选学习资料 - - - 欢迎下载精品学习资料（二）引导词1. the newsthat mr. li will be our new english teacher is true.2. he hasn t made the deciw sih on etherhe will go there.3. the questionwhoshould do the work is being discussed at

48、 the meeting.4. i have no ideawhat the boy is doing in the next room now.5. we havenytet settled the question where we are going to spend our summervacation this year.6. i have no ideahow i can get to the railway station.7. i have no ideawhen he will be back小结：that 引导同位语从句时无词义,也不充当任何成分,但通常不行以省略,如句 1

49、； whether 引导同位语从句时意为 “为否”,通常不能用 if 来代替 、 如句 2; 连接代词 who、 what 等可以引导同位语从句,如句3, 4； 连接副词 where、 how、 when等可以引导同位语从句, 如句 5,6,7；三 that 引导的同位语从句和定语从句 意义不同：同位语从句用来进一步说明前面名词的内容；而定语从句用来修饰.限定前面的先行词；试比较：1. the news that our team has won the final match isencouraging.2. the news that you told us is really encou

50、raging. that 的功能不同： that 引导同位语从句时为一个纯连词, 不充当任何成分； 而引导定语从句时, 不仅起连接作用, 而且仍指代先行词并在从句中充当主语. 宾语等成分；试比较：1. dad made a promise that he would buy me a cd player if i passed the englishtest.2. dad made a promise that excited all his children. 可否省略： that 在引导同位语从句时,通常不行省略；在引导定语从句时,如在从句中作宾语,通常可以省略,如作主语就不行以省略；主语

51、从句1 由连词 that 引导的主语从句 : 引导词 that 无含义 、在句中不做成分 、不行以省；that you will win the medal seems unlikely. 你想获得奖牌看起来为不行能的；2 用连词 whether 引导的主语从句 : whether有含义 为否、在句中不做成分 、不行以省；whether she is coming or not doesnt matter too much.她来不来都无关紧要；3 用连接代词引导的主语从句 在由连接代词 who、 whose、 whom、which、 what、 whoever、 whomever、 which

52、ever、 whatever引导的名词性从句中,其连接代词在句中起名词性作用,担当肯定成分.what you need is more practice.精选学习资料 - - - 欢迎下载精品学习资料你所需要的为更多的训练；whatever we do is to serve the people.我们无论做什么都为为人民服务；4 用连接副词 when、 where、 why、 how引导的名词性从句 其连接副词有含义 、在句中作状语； where we should leave it is a problem.留意1. it 做形式主语 、而将主语从句放在句末（特殊为当谓语较短时）； tha

53、t light travels in straight lines is known to all.=it is known to all that light travels in straight lines.众所周知光沿直线传播；当 what 引导的主语从句表示 “ 的东西 ” 时,一般不用 it 作形式主语； 错:it is a book what he wants.对:what he wants is a book. 他想要的为本书；固定用法和译法（ 1 ） it is +名词 +从句it is a fact that事实为it is good news that为好消息it is

54、a question that为个问题it is common knowledge that为常识类似的名词仍有： a pity；a wonder；a good thing； no wonder； surprise等；（ 2 ） it is +形容词 +从句it is necessary that有必要it is clear thatit is likely that很 清 楚很可能it is important that重要的 为类似的形容词仍有： strange; natural; obvious; true; good; wonderful; possible;精选学习资料 - - -

55、欢迎下载精品学习资料unlikely; quite; unusual; certain; evident; worth-while; surprising;interesting;astonishing、 etc.（ 3 ） it is +过去分词 +从句it is said that据说it is reported that据 报 道it has been proved thatit must be proved that已 证 明必需指 出类似的过去分词仍有： known; estimated; expected; believed; thought; hoped; noted;discu

56、ssed; required; decided; suggested; demanded; made clear; found out、；etc.当“ 及物动词+ 宾语” 较短时,也可用这种结构；it shocked me that peter did not tell anybody where he was.让我惊讶的为彼得没有告知任何人他在哪里；2.只用 whether 不用 if 引导主语从句 .表语从句一. 在复合句中作表语的从句 、 就叫做表语从句； 表语从句一般放在系动词之后 、结构为 “主语+系动词 +表语从句 ”；连系动词： be动词.表示连续的系动词 （keep、 rema

57、in、 stay ） .感官动词 feel摸起来,感觉 、 smell闻起来 、 sound听起来 、 taste尝起来,吃起来 等.表示变化的系动词（become、 grow、 turn、 fall、 get、 go）、 .表终止的系动词 prove、 turn out结果为,证明为 .seem、 appea（r看起来 ）连系动词通常不用于被动语态和进行时态中；he has become what he wanted to be ten years ago.他已经成为了他 10 年前想成为的；his suggestion is that we should stay calm.他的建议为,我

58、们应当保持冷静；精选学习资料 - - - 欢迎下载精品学习资料二表语从句的引导词1.从属连词： that / whether /as if /as though/as/because(1) that 引导表语从句本身没有词义,在句中只起连接作用,不充当句子成分,一般不能省略；that fact is that more than seventy percent of the earths surface is covered by wat连接词 that 一般不能省略,但当主句中含动词do的某种形式时, that 可以省略；what i want to do is that i can go

59、up to him and thank him. 我想做的事为走到身边去感谢他；(2) whether 引导表语从句表示 “为否”但、不充当句子的成分；the question is whether we can finish our work by tomorrow evening.if 与whether均意为 “ 为否” ,但引导表语从句时,只能用whether、 不能用 if；(3) as if/though 似乎“ ” ,引导表语从句时要留意语态.假如句中的情形与事实不相符,从句多用虚拟语气； 假如从句表示与现在事实相反、谓语动词用一般过去式；假如从句表示与过去事实相反时、谓语动词要用“ had+ 过去分词” ,假如从句表示将来的可能性不大,用would might 、could +动词原形.li lei is now in a new jacket. he looks as if hewerean american boy. 现在事实相反the girl is giving us a vivid description of the moon. it seems as if shehad been tothe moon