虛擬語氣是高考英語必考的語法點，其遍佈在聽力、閱讀、完形、語法填空、寫作等各個題型中。今天，就和小簡老師一起來學習學習虛擬語氣吧！
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一、虛擬語氣的概念
虛擬語氣包含兩種：一種指與事實相反或不可能發生。“虛擬條件句+虛擬主句”的結構都屬於這一類；even if、even though、as if、as though引導的狀語中如果需要用到虛擬語氣也屬於這一類；wish、would rather後面接的賓語從句表示不可能實現的願望，還是屬於這一類。
另一種指與事實實際是否發生沒有直接關係。如suggest、order、demand等表示建議、命令、要求等相關的名詞性從句都屬於這一類。
二、名詞性從句中的虛擬語氣
1.表達和建議、要求、命令、主張等含義相關的名詞性從句，一律用主語+should+動詞原形（should可以省略）結構。具體涉及到這些動詞以及它們的名詞形式：
一堅持（主張）：insist
二命令：order，command
三要求：require，request，demand
四建議：suggest，advise，propose，recommend
例如：
It was suggested that he（should）join in the club activities.（主語從句）
I suggested that he（should）join in the club activities.（賓語從句）
I had an suggestion that he（should）join in the club activities.（同位語從句）
My suggestion was that he（should）join in the club activities.（表語從句）
這四句話表達同一個意思：我建議他加入這個俱樂部的活動。
2.表示重要性、必要性、吃驚等時，一律用it is+形容詞+that+主語+should+動詞原形（should可以省略）結構。
例如：
It's important that you (should) study English hard.
努力學習英語是很重要的。
It's necessary that you (should) praise your students as much as possible.
儘可能多的表揚你的學生是有必要的。
It is strange that she (should) not have been invited.
很奇怪她竟然沒有被邀請。
3. ① wish 後面所跟的賓語從句，其謂語動詞用虛擬語氣（意為“要是/但願…就好了”），其形式主要有三種：表示對現在情況的虛擬：wish+一般過去時的賓語從句；表示對過去情況的虛擬：wish+ 過去完成時的賓語從句；表示對將來情況的虛擬：wish+would/could+動詞原形。
I wish it were spring all year round.
我希望一年四季都是春天。
I wish it would be fine tomorrow.
我希望明天天氣好。
She wished she had stayed at home then.
她希望她當時待在家裡。
if only 後接從句也用虛擬語氣，其形式與wish的用法一致。
② would rather 後面所跟的賓語從句，其謂語動詞用虛擬語氣（意為“寧願......”），其形式主要有兩種：表示對現在/將來情況的虛擬：wish+一般過去時的賓語從句；表示對過去情況的虛擬：wish+ 過去完成時的賓語從句
三、虛擬條件句中的虛擬語氣
1.表示與現在事實相反的情況
從句：If+主語+did(be動詞用were)
主句：主語+ should/would/might/could+do
If there were no air or water,there would be no living things on the earth.
如果沒有水和空氣，地球上就不會有生物。(事實：地球上既有空氣也有水)
If I were you,I would take an umbrella.
如果我是你，我會帶把傘。（事實：我不可能是你）
If I knew his telephone number,I would tell you.
如果我知道他的電話號碼，我就會告訴你。（事實：不知道）
2.表示與過去事實相反的情況
從句：If+主語+had+done
主句：主語+should/would/might/could+have done
If he had taken my advice,he would not have made such a mistake.
如果他聽我的勸告的話，就不會犯這樣的錯誤了。（事實：沒有聽我的話）
If I had got there earlier,I should/would have met her. 如果我早到那兒，我就會見到她。（事實：去晚了）
3.表示與將來事實相反的情況
從句：①if+主語+were to do
②if+主語+should+do
③if+主語+過去式（be動詞用were）
主句：主語+should/would/might/could+do
If he should come here tomorrow,I would talk to him.
如果他明天來這兒的話，我就跟他談談。（事實：不可能來）
If she were to be here next Monday,I would tell her about the matter.
如果她下週一來這兒的話，我就會告訴她這件事的始末。（事實：不可能來）
If there were a heavy snow next Sunday,we would go skating.
如果下週日下大雪，我們就去滑冰。（事實：不可能下雪）
注意事項：
① 錯綜時間句：即虛擬條件狀語從句與虛擬主句中謂語動作的時間不一致。
If he knew her,he would have greeted her that day.
如果他認識她的話，他肯定會去問候她了。
If they had informed us,we would not come here now.
如果他們通知過我們的話，我們現在就不會來這裡了。
If I had worked hard at school,I would be an engineer,too.
如果我在學校學習刻苦的話，我現在也會成為一個工程師了。
② 虛擬條件句中的省略：當虛擬條件句的謂語動詞含有were,should,had 時，if 可以省略，這時條件從句要用倒裝語序，即把were,should,had等詞置於句首，這種多用於書面語。
Should he agree to go there,we would send him there.
要是他答應去的話，我們就派他去了。
Had he learnt about computers,we would have hired him to work here.
如果他懂一些電腦知識的話，我們已經聘用他來這裡工作了。
Were she here,she would agree with us.
如果她在這兒的話，她會同意我們的。
③ 用其它形式表達虛擬條件：虛擬條件狀語從句有時不表達出來，只暗含在副詞、介詞短語、上下文或用其它方式表示出來。如without…，but for…（要不是...）等。
But for his help,we would be working now.
要不是他的幫助，我們還會在工作呢。
We didn't know his telephone number,otherwise we would have telephoned him.
我們不知道他的電話號碼，否則我們就會給他打電話。
Without your instruction,I would not have made such great progress.
要是沒有你的指導，我不會取得如此大的進步。
④ 在虛擬語氣的從句中，動詞be的過去時態一律用were，不用was。
If I were you,I would go to look for him.
如果我是你，就會去找他。
⑤ 在虛擬條件句中，should/would/might/could四個詞只能用should；在虛擬主句中，主語只有是第一人稱時，才能用should。
If he had got there earlier, he would have met her.
如果我早到那兒，我就會見到她。
If I had got there earlier,I should/would have met her.
如果我早到那兒，我就會見到她。
四、其它從句中的虛擬語氣
1.虛擬語氣用在狀語從句中
① 由as if 或 as though 所引導的方式狀浯從句，若從句與事實相反，則要用虛擬語氣。其形式如下：
② 由 even if 或 even though 所引導的讓步狀語從句，若從句與事實相反，則從句和主句都要用虛擬語氣。其形式如下：
2.虛擬語氣用在定語從句中
在it is (high) time that…句型中也用虛擬語氣，從句常用過去式，有時也用should+動詞原形，表示該做而沒做的事，含建議的意味。
It is time that we went home.=It is time that we should go home.
我們該回家了。
It is time we left. =It is time we should leave.
我們該走了。
It is time we summed up our results.= It is time we should sum up our results.
我們該總結我們的成績了。
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