主语从句详解Word格式文档下载.docx
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=Ithasnotbeenannouncedwhentheplaneistotakeoff.
（但当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:
Itisabookwhathewants.
对:
Whathewantsisabook.
另外,需要注意的是,it作形式主语代替主语从句时,要注意和as引导的定语从句的区别.试比较：
ItwasreportedthattheUSwasundertheterroristattack.
Aswasreported,theUSwasundertheterroristattack.
（2）常见用it作形式主语的复合句结构
A.Itis+名词+从句
Itisafactthat…事实是……
Itisgoodnewsthat………是好消息
Itisaquestionthat………是个问题
Itiscommonknowledgethat………是常识
类似的名词还有：
apity；
awonder；
agoodthing；
nowonder；
surprise等.
Itisamysterytomehowitallhappened.
Itiscommonknowledgethatthewhaleisnotafish.
ItisnosurprisethatBobshouldhavewonthegame.
It’sapitythatyoumissedthefilm.
B.Itis+形容词+从句
Itisnecessarythat…有必要……
Itisclearthat…很清楚……
Itislikelythat…很可能……
Itisimportantthat…重要的是……
类似的形容词还有：
Strange;
natural;
obvious;
true;
good;
wonderful;
possible;
unlikely;
quite;
unusual;
certain;
evident;
worth-while;
surprising;
interesting;
astonishing,etc.
Itisdoubtfulwhethershewillbeabletocome.
Itwasreallyastonishingthatherefusedtotalktoyou.
Itisessentialthatheshouldbeherebytheweekend.
Itseemsobviousthatwecannotgoonlikethis.
Itisnecessarythatyou（should）masterthecomputer.
ItisimportantthatastudentlearnEnglishwell.
Itislikelythatahurricanewillarrivesoon.
需要注意的是,这类主语从句中,谓语动词很多为“（should）＋动词原形”,即要用虚拟语气.
C.Itis+过去分词+从句
Itissaidthat…据说……
Itisreportedthat…据报道……
Ithasbeenprovedthat…已证明……
Itmustbeprovedthat…必须指出……
类似的过去分词还有：
known;
estimated;
expected;
believed;
thought;
hoped;
noted;
discussed;
required;
decided;
suggested;
demanded;
madeclear;
foundout,etc.
Itisthoughtthatheisthebestplayer.
Itisestimatedthatthevaseis2000yearsold.
Itisusedtobethoughtthatanewstarmustbeduetoacollisionbetweentwostars.
Ithasnotbeenmadeclearwhenthenewroadistobeopenedtotraffic.
Itissaidthathewaskilledintheearthquake.
D.Itseems（happened/appears/doesn’tmatter/makesnodifference/occurred…）that…
Itseemsthattheywillwinthegame.
Itmakesnodifferencewhetherhewillattendthemeetingornot.
ItdoesnotmatterifImissedmytrain.
IthappenedthatIsawhimyesterday.
主从练习
1._____
as
much
one-fifth
of
all
timber
harvested
is
not
used.
A.
The
estimate
B.
estimated
C.
They
are
D.
It
that
2.
_____
some
mammalscame
to
live
in
the
sea
known.
Which
B.
Since
Although
D.
How
3.
we
have
achieved
attributed
guidance
our
parents.
Whoever
Whatever
However
That
4.
wealthy
does
necessarily
mean
that
a
man
greedy.
For
reason
he
Just
because
being
5.
___
happened
this
developed
country
sounds
like
science
fiction,
it
could
occurelsewhere
world.
which
what
how
it
6.
she
had
forgotten
take
her
notebook.
occurred
She
To
7.
I
am
sure
said
wrong.
what
8.
We
lost
way
forest,
and
____
made
matters
worse
was
getting
dark.
What
9.
or
still
uncertain.
He’s
coming
If
C.
Whether
he’s
coming
10.
It’s
he’ll
be
able
come.
doubt
whether
doubtful
11.
______
at
work
heart
big
city
home
quiet
suburb,
Dick’s
life
tied
machines.
Till
Unless
12.
saw
both
surprised
frightened
him.
When
What
Which
13.
warm
sunshine.
do
need.
need
need
14.
pity
should
feel
so
upset.
He
It
15.
spoonful
soil
can
tell
us
about
structure
early
history
moon.
Remarkable
Quite
remarkably
remarkable
fact
16.
you
nominate
will
elected.
Who
Whom
Whomever
That’s
17.
book
borrow
must
returned
within
week.
Whichever
18.
gets
first
starts
cooking.
Anyone
1.________makesmistakesmustcorrectthem.
A.WhatB.ThatC.WhoeverD.Whatever
2.Itworriedherabit____herhairwasturninggrey.
A.whileB.thatC.ifD.for
3.Whenandwhyhecamehere________yet.
A.isnotknownB.arenotknown
C.hasnotknownD.havenotknown
4.________isnoreasonfordismissingher.
A.Becauseshewasafewminuteslate
B.Owingtoafewminuteslate
C.Thefactthatshewasafewminuteslate
D.Beingafewminuteslate
5.________Tomlikedtoeatwasdifferentfrom________.
A.That…thatyouhadexpectedB.What…thatyouhadexpected
C.That…whatyouhadexpectedD.What…whatyouhadexpected
6.________wegoswimmingeveryday________usalotofgood.
A.If...doB.That...doC.If...doesD.That...does
7.It________Bobdrivesbadly.
A.thinksthatB.isthoughtwhatC.thoughtthatD.isthoughtthat
8.It'
suncertain________theexperimentisworthdoing.
A.ifB.thatC.whetherD.how
9.________theboydidn'
ttakemedicinemadehismotherangry.
A.ThatB.WhatC.HowD.Which
10.____wecan'
tgetseemsbetterthan____wehave.
A.What,whatB.What,thatC.That,thatD.That,what
11.____youdon'
tlikehimisnoneofmybusiness.
A.WhatB.WhoC.ThatD.Whether
12..____we'
llgocampingtomorrowdependsontheweather.
A.IfB.WhetherC.ThatD.Where
13._________isgoingtodothejobwillbedecidedbythePartycommittee.
A.ThatB.WhyC.HowD.Who
14._______we'
llfinishtranslatingthebookdependsonthetime.
A.WhenB.WhyC.WhatD.That
15.______hewon'
tgothereiscleartoallofus.
A.HowB.WhatC.WhyD.This
16.______thehousewillbebuiltwillbediscussedattomorrow'
smeeting.
A.IfB.WhereC.ThatD.What
17._______youcomeornotisuptoyou.
A.WhatB.IfC.WhyD.Whether
18._______makesmistakesmustcorrectthem.
A.WhoB.AnyoneC.WhoeverD.Anybody
19._______teamwillwinthematchisamatterofpublicconcern.
A.WhichB.ThatC.IfD.How
20.Whoisthisfactory__________someforeignfriendsvisitedlastFriday?
A.thatB.whereC.whichD.theone
21.Isthisfactoryyouvisitedtheotherday?
A.thatB.whereC.inwhichD.theone
22.________leavestheroomlastoughttoturnoffthelights.
A.AnyoneB.ThepersonC.WhoeverD.Who
表语从句
1、概述
用作表语的从句叫作表语从句,它位于主句中的连系动词之后.引导表语从句的词有从属连词that、whether、asthough（if）；
关系代词who,what,which,whom,whose,whatever,whoever,whomever,whichever等；
关系副词when,where,why,how,however,whenever,wherever等.可以接表语从句的连系动词由be,look,remain,seem等.That引导表语从句时,在口语中,间或可以省略.
Thetroubleisthatweareshortofmoney.困难是我们资金短缺.
ThatiswhystonewallsareusedinsteadoffencesaroundNewEnglandfields.这就是为什么在新英格兰用石头墙而不用栅栏的原因.
Atthattime,itseemedasifIcouldn'
tthinkoftherightwordanyhow.当时,我似乎怎么也想不出一个恰当的字眼来.
2、由从属连词that,whether引导的表语从句.
that在引导表语从句时无词义,而whether有词义,意为、“是否”.这时主句的主语常常是些抽象名词,如question（问题）,trouble（麻烦）,problem（问题）,result（结果）,chance（可能性）,suggestion（建议）,idea（想法）,reason（理由）等.表语从句对主句主语进行说明、解释,使主语的内容具体化.
Thetroubleis（that）shehaslosthismoney.麻烦的事是他丢了钱.
Thequestioniswhetherweneedmoreicecream.问题是我们是否还需要一些冰淇淋.
Theproblemwasthatitwastoovaluableforeverydayuse.问题是它作为日常之用太贵重了.
Whatshecouldn’tunderstandwasthatfewerandfewerstudentsshowedinterestinherlessons.我们不能理解越来越少的学生对他的课不感兴趣.
3、由关系代词引导的表语从句.
关系代词who,what,which,whom,whose,whatever,whoever,whomever,whichever等
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