A. 英語語法 關於If引導的條件狀語從句或虛擬語氣
If i were on the spot that day,I would have been able to prevent the disaster from happening,
這句話地意思是：如果那天是我在當班，我就能夠阻止災難的發生了。
這里用的的確是虛擬語氣，虛擬的也是過去的時刻發生的事，但是並不是過去的事情都得用過去完成時來表虛擬，這里用were 並沒有錯
但是 你如果用完成時也是可以的：If i had been on the spot that day,I would be able to prevent the disaster from happening,這個句子也是對的
這兩個都是虛擬的過去，但是並非二者選其一，兩個都是對的啊
你舉得這個例子：If I were not busy, I would have come.也表過去
如果我不忙（過去的某個時間），我就去了
下面這兩個句子應該會對你有啟發：
If I were you, I would have taken his advice.我要是你，我就採納了他的建議。（從句指現在，主句指過去）
If the weather had been more favorable, the crop would be growing still better.如果氣候更適宜一些，莊稼會長得更好。（從句指過去，主句指現在）
ps：if I were you ，I would take this answer.
希望採納
B. 條件狀語從句、時間狀語從句、賓語從句的語法（要全）急急急！！！！
你好,以下是你要的最全面的資料,對你定有幫助.
一. 時間狀語從句:
學習狀語從句的重點是連接從句的連詞的選擇，就比如時間狀語從句吧。
The new secretary is supposed to report to the manager as soon as she________.
A.will arrive B.arrives C.is going to arrive D.is arriving
在時間狀語從句中，當主句是將來時或含有情態動詞時，從句通常用一般現在時代替將來時。選（B）每當他們遇到困難時，我們就去幫助他們。
We will go to help them whenever they meet with difficulties
可以引導時間狀語從句的詞很多，比如when ,wile,as等等。
When ,while,as的區別
I was reading a novel________he watching TV.
A.when B.while C.before D.as 2
While表示一段時間並表示對比，從句中不能用點動詞；when還可以表示從句動作發生在主句動作之前或之後；as表示「一邊。。。。。一邊。。。。。」
While表示對比不只可以用在時間狀語從句中。
Some people like coffee,while others like tea.有人喜歡咖啡，而有人則喜歡茶，強調了對比。When you have finished your work,you may have a rest.當你工作做完的時候，你可以休息一會兒。從句的finish發生前，才會有rest(休息)這個動作發生。在這種情況下，就只能用when,而不能用while或as,除此以外，when還有一點比較特殊。
When可以表示「那時突然」的意思，而其他兩個詞則還可以，比如說，我在看電視的時候，他突然進來了，就可以說：I was watching TV,When he suddenly came in.
As通常表示「一邊。。。一邊」的意思，比如我邊洗碗邊唱歌就可以說「As I was washing the dishes,I was singing songs.」另外，它還可以表示」「隨時間推移」，這就是它的特殊之處了。
You will grow wiser as you grow older.
引導時間狀語的從句還有before,after,once,until等。這個until的用法也需要注意，下面我們就來看看它該怎麼用吧。
People don』t know the value of freedom________they have lost it.
A. until B.when C.since D.as
till和until表示「直到。。。。。。才。。。。。。」要和延續性動詞連用，not….until是固定搭配。
Not….until……√ not….till,而且until可用於句首，而till通常不用於句首，比如：Until you told me,I had heard nothing of what happened。
直到你告訴我，我才知道出了什麼事
還有幾個連接時間狀語從句的關聯詞，表示「一…..就。。。。」的結構，他們是：as soon as,the moment,no sooner….than ,hardly/scarcely….when. Tony,這些關聯詞你用用嗎？
值得注意的是這幾個關聯詞的量才而為和語序的不同用法。量才而為上，as soon as和the moment所在的復合句中，主句和從句通常都用過去時，no sooner…..than和hardly/scarcely…when所在的復合句中，主句一般用過去時，而從句用過去完成時。
________had he gone to bed. ________he fell asleep.
A. The moment,/ B.No sooner,than C.When,hardly D.As soon as,/
當no sooner或者hardly在句首時，從句要倒裝。
我剛一到家，就開始下雨了。
As soon as I got home,it began to rain.
The moment I got home,it began to rain.
Ihad no sooner got home than it began to rain.
Hardly had I got home when it began to rain.
no sooner….than和hardly….when說一下，至少要一句倒裝啊。
二、條件狀語從句。
You will be late__________you leave immediately.
A. unless B.until C.if D.or
B.
Unless=if not. If you don』t leave immediately you will be late.
在條件狀語從句中，如果主句是將來時或含有情態動詞，從句通常用一般現在時代替將來時。這只有在時間和條件狀語從句中才有這個用法。
條件狀語從句還可以由as long as(只要),in case(以防)，on condition that(條件是)等詞來引導。
You may do anything you like as long as it is not against the law.只要不犯法，你可以做任何你喜歡的事。
Take this umbrella with you in case it rains.帶上這把十倍雨傘，以防下雨。
三、賓語從句
引導賓語從句時，whether和if一般可以互換。If和whether直接就可以引導賓語從句了，不用that了。
可是並不是在所有的賓語從句中if和whether都可以互換。它們也是有區別的。
如果出現or not則只能用whether。
比如：We don』t know whether he will come or not.我們不知道他是否會來。在這句話里只能用whether.
介詞賓語從句只能用whether。
比如：That depends on whether he will come.那取決於他是否會來。
賓語從句還有和主語從句不一樣的地方。我們看一看吧。
8.________ I should take part in the sports meet?
A.Do you think why B.Do you think when C.Do you think D.Do you think how
C
引導賓語從句的that在從句中不充當任何成分時，可以省略。
不過不是所有引導賓語從句的that都可以省略。
第一，如果有兩個並列的由that引導的賓語從句由and或but連接，那麼第一個that可以省略，但第二個that不能省略。
比如：He said(that)he liked to live in China and that he wouldn』 t leave for America.
他說他喜歡住在中國而不會去美國。
第二點是如果that引導的是介詞賓語從句，則that不能省略。
例如：你的作文寫得不錯，只是有幾個拼寫錯誤。就應該說
Your composition is quite good except that are some spelling mistakes.
這里的that引導的從句作介詞except的賓語，連接詞that就不可以省略。
也就是說主語從句的that不可以省略，而賓語從句的that卻在大多數情況下可以省略。
主語從句和賓語從句也有相同的地方。
名詞性從句之間是有些共性的，下一個秘訣和主語從句的也很相似。
9 We think________important that college students should master at least one foreign language.
A.it B.him C.that D.what
A
主句的賓語是「賓語＋賓補」的復合賓語時，要用形式賓語it替代賓語從句，而將賓語從句置於賓補之後。
再比如：我認為所有的人都應該尊重老人，這是非常正確的。
I think it quite right that all of us should respedt the old.
10.I don』t think you are right,____?
A.aren』t you B.are you C.do I D.do you
B
這是通過反意疑問句來說明賓語從句的否定情況，動詞think, believe, suppose, expect等詞後面的賓語從句帶有否定含義時，通常不否定賓語從句中的謂語，而是否定主句的謂語動詞。
這種下的反意問句要根據從句的真正意思來提問。
再來練習一下。
我想他不會來 I don』t think he will come.
11.No one can be sure________in a million years.
A.what man will look like B.what will man look like
C.man will look like that D.what look will man like
A
Sure,afraid,glad,certain等形容詞後面可以接賓語從句。
這幾個形容詞的後面通常都是接介詞of的。
比如I』m afraid of being late.如果轉換成賓語從句就是I』m afraid that I』ll be late.
再比如I am sure that you will come.我確信你會來。
賓語從句：陳述語序
形式賓語
if和whether的區別
在某些動詞和形容詞後的用法
C. 英語的條件狀語從句咋寫
條件狀語從句可分為真實性和非真實性（虛擬語氣）兩種。
真實性條件狀語從句：內主句用一般將容來時，條件狀語用一般現在時，if
it
rains
tomorrow
we
won't
go
to
the
beach.也不是絕對的，也有一些變形
主句也可以是祈使句，例如please
come
to
my
party
if
you
have
time.
主句也可是情態動詞，例如you
can
take
a
nap
if
you
are
tired.
從句也可是現在進行時例如，if
he
is
working
i
won't
disturb
him.
D. 英語中：條件句和條件狀語從句區別
沒區別的。
條件句就是條件狀語從句，條件句不可能當主句。
E. 英語中條件狀語從句分幾種
狀語從句分九種，條件狀語從句應該分真實條件和虛擬條件吧
F. 英語中什麼是條件狀語從句
由連接詞if或unless引導的狀語從句叫做條件狀語從句。
引導條件狀語從句最內常用的連詞是if，由if引導的容條件狀語從句表示在某種條件下某事很可能發生。例句：If
I
want
an
apple,
my
mother
will
give
one
to
me.
除了if之外,還有很多詞引導條件狀語從句，但是出現的頻率較小，就幾個例子吧：
unless
除非,若不,除非在……的時候;
on
condition
(that)...
在……條件下,如果;
supposing
如果,假如;
provided
假如,除非,以……為條件.
G. 英語中的條件狀語從句
連接詞主要有
if,
unless,
as/so
long
as,
on
condition
that
等。.
if
引導的條件句有真實條件句和非真實條件句兩種。非真實條件句已在虛回擬語答氣中闡述。
unless
=
if
not.
Let's
go
out
for
a
walk
unless
you
are
too
tired.
If
you
are
not
too
tied,
let's
go
out
for
a
walk.
典型例題
You
will
be
late
___
you
leave
immediately.
A.
unless
B.
until
C.
ifD.
or
答案A。
句意：除非你立即走，否則你就回遲到的。可轉化為
If
you
dong
leave
immediately,
you
will
be
late.B、D句意不對，or表轉折，句子如為
You
leave
immediately
or
you
will
be
late.
H. 英語if引導的條件狀語從句重點
學習" if " 引導的條件狀語從句的用法,現在總結一下:
if 條件句不一般,幾個要點記心間;
條件句,放在前,逗號要放句中間。
條件句表可能，主句多用將來時；
條件句表事實，主句常用現在時。
在 if 引導的條件狀語從句中，如果從句談論的是一個有可能發生的事實及其產生的相關的結果，主句用一般將來時態，從句用一般現在時態。如：
We can walk there if we can't find a bus .
If it rains tomorrow ,we will not go to the zoo.
What will you do if you find a panda in danger.
如果 if 條件句談論的是重復發生和預示要發生的情景和事件，則主從句大多用一般現在時態。如：
If bears are in danger ,they attack people.
注意 ：
在 if 引導的條件狀語從句中，if 和條件句位置靈活，可直接放在主句後面，若 if 條件句放句首，
從句後面要加逗號，和主句隔開。
還要注意前後時態一致原則
I. 英語中從句的語法大全
英語中六大從句用法總結
1.主語從句
1）主語從句可直接位於主語的位置，如果從句較長，謂語又較短，可用it作形式主語，而將從句放在句末。常見的句型有：
*It is a fact\a pity\a question\good news that...
*It seems\appears\happened\has turned out that...
*It is clear\important\likely\possible that...
*It is said\reported\estimated\has been proved that...
It is said that comic books create a connection between people of the same generation.
It seems that the performance is very useful.
2)what引導的主語從句表示「...的東西時」，一般不用it作形式主語。
What we lack is experience.
3)what,who,when,why,whether等詞含有各自的疑問意義，但它們引導的主語從句，都用陳述語序。
How the plan is to be carried out should be discussed again.
I did know why I felt like crying.
2.賓語從句
1）賓語從句可位於及物動詞、介詞和某些形容詞後。連詞that常可省略。介詞後一般接疑問詞引導的賓語從句。in that(因為),except that(除了),but that(只是）已構成固定搭配，其他介詞後一般不接that引導的賓語從句。
*I promised that I would change the situation.
*All this is different from what American young people would say about friendship.
*He is certain that watching so much television is not good for children.
*This article is well-written except that it is a bit too long.
2)賓語從句後如有賓補，要用形式賓語it來代替，而把賓語從句移至賓補之後。
He has made it clear that he would not change his mind.
3)在think,believe,suppose,expect等動詞後的賓語從句中，如果謂語是否定的，一般將否定詞移至主句謂語上，賓語從句則變成肯定形式。
He didn't think that the money was well spent.
3.表語從句
表語從句出現在結構為「主語+系動詞+表語從句」的句子中。表語從句除可用that,what,when,why,whether,how等引導外，還可由because,as if(though)等引導。that常可省略。如主句主語為reason,只能用that引導表語從句，不可用because.
Perhaps the most important thing to remember is that there is no one common type of life in America.
The reason why so many people died there is that there were not enough food supplies.
It looks as if successful international cultural communication will make the world smaller.
4.同位語從句
同位語從句用於對前面出現的名詞作進一步說明，一般用連詞that引導，由於先行名詞的意義不同，也可用whether,who,when,where,what,why,how等引導。常見的先行名詞有fact,idea,belief,news,hope,conclusion,evidence,suggestion,order,problem,report,decision.有時由於謂語較短，將同位語從句位於謂語之後。
She finally made the decision that she would join the fashion show.
I had no idea how many books I could borrow at a time.
The news came that their team had won the championship.
5.定語從句
定語從句所修飾的先行詞可以是名詞或代詞，也可以是一個句子。定語從句通常位於先行詞之後，由關系代詞或關系副詞引導。
*限制性定語從句
限制性定語從句修飾先行詞，對先行詞起修飾作用，緊接先行詞之後，無逗號，若省去，原句意思不完整。引導定語從句的關系代詞有who,whom,whose,which,that等。who,whom,whose用於指人，whose有時也可指物，相當於of which；which用於指物；that既可指人也可指物，但只用於限制性定語從句中。關系代詞除了引導定語從句，替代先行詞外，還在從句中擔任主語、賓語、定語等。
The computers and cables which make up the Internet are owned by people and organizations.
Those who live alone or who are sick may have trouble in getting close to other people.
The girl whose parents died in an accident is living with her grandmother.
1)當先行詞是all,anything,everything,something,nothing等不定代詞或先行詞前有first,last,any,few,much,some,no,only以及形容詞最高級修飾時，只能用關系代詞that引導從句。
That is all that I've heard from him.
He's the first person that I'm going to interview this afternoon.
2)關系代詞的省略
在從句中作賓語的關系代詞常可省略。關系代詞緊跟介詞，作介詞賓語時不可用that，只可用which或whom引導從句，並且不可省略，但當介詞位於賓語從句句末時，作為介詞賓語的關系代詞仍可用that，也可省略。
This is one of those things with which we have to put up.
This is one of those things (which\that) we have to put up with.
3)引導定語從句的關系副詞有when,where,why等。關系副詞在從句中作狀語，意義上相當於一個「介詞+which」的結構。
Even in comic books where(=in which) there are no words,the stories are fully expressed through the drawings.
No one knows the reason why(=for which) he was so angry that day.
5.定語從句
*非限制性定語從句
非限制性定語從句既可修飾先行詞，也可修飾整個主句，起補充說明作用，與主句之間有逗號隔開，若省去，原句意思不受影響。不可用that引導非限制性定語從句。關系詞不可省略。
Every object has a gravitational pull,which is rather like magnetism.
*「介詞+which\whom\whose」引導的定語從句
「介詞+which\whom\whose」可引導限制性定語從句，也可引導非限制性定語從句，該結構中介詞的選擇取決於從句謂語動詞的固定搭配，或先行詞的習慣搭配。
This is the computer on which he spent all his savings
It is written by a person with whom we are all familiar.
*as引導的定語從句
as引導的定語從句主要用於「such...as」及「the same...as」的結構中，代替先行詞是人或物的名詞。as引導非限制性定語從句時，代替整個主句，從句可位於主句之前、之後或中間。
These are not such problems as can be easily solved.(as代替先行詞problems)
As is mentioned above,no single company or group can control what happens on the Internet.(as代替主語)
6.狀語從句
*時間狀語從句
引導時間狀語從句的從屬連詞和片語有：
1）when,whenever,while,as,after,before,since,till,until,once等。
We have learnt quite a lot about it since we came here.
2)as soon as,hardly(scarcely)...when,no sooner...than,each(every) time,the moment,immediately(that)等。
As soon as I sent an e-mail message,I received positive responses.
The moment he heard the good news,he jumped with joy.
*地點狀語從句
引導地點狀語從句的連詞是where,wherever.
Wherever she went,she took her little daughter with her.
*原因、結果和目的狀語從句
1）引導原因狀語從句的從屬連詞有：because,as,since,now(that),seeing that,considering that,in that等。
Considering that he is a freshman,we must say he is doing well.
2)引導結果狀語從句的連詞有：so...that,such...that
,so that,that,so等。
Mickey Mouse is so attractive that the children are reluctant to leave.
3)引導目的狀語從句的連詞有：so that,in order that,for fear that,lest等，從句常使用may,might,can,could,would等情態動詞。
We got up early this morning so that we could catch the first bus to the railway station.
*條件和讓步狀語從句
1）引導條件狀語從句的連詞和片語有if,unless,as(so) long as,on condition that,in case,provided(providing) that,supposing等。
As long as you have the right equipment,you can use a telephone line to transmit computer data.
2)引導讓步狀語從句的連詞和片語有though,although,whether,even though,even if,no matter what(when,how...),whatever(whenever,wherever,however....)等。though,even if等引導狀語從句可轉換成含有as的部分倒裝結構，具有強調意義。其結構為「形容詞（副詞、動詞、名詞）+as+主語+謂語」。
No matter what you may say,I would not change my mind.
Young as he is,he is quite experienced in this work.(=though he is young)
Child as he is,he can speak English fluently.(=though he is a child)
*方式狀語從句
引導方式狀語從句的連詞有as,just as,as if,as though等。as if,as though引導的狀語從句中，謂語動詞常用虛擬語氣，表示與事實相反。
The young man made the experiment just as the teacher had taught him.
Everything went on as usual as if nothing had happened.