虛擬語(yǔ)氣
1) 概念
虛擬語(yǔ)氣用來(lái)表示說話人的主觀愿望或假想，所說的是一個(gè)條件，不一定是事實(shí)，或與事實(shí)相反。
2) 在條件句中的應(yīng)用
條件句可分為兩類，一類為真實(shí)條件句，一類為非真實(shí)條件句。非真實(shí)條件句表示的是假設(shè)的或?qū)嶋H可能性不大的情況，故采用虛擬語(yǔ)氣。
16.1 真實(shí)條件句
真實(shí)條件句用于陳述語(yǔ)氣，假設(shè)的情況可能發(fā)生，其中 if 是如果的意思。
時(shí)態(tài)關(guān)系
句型： 條件從句 主句
一般現(xiàn)在時(shí) shall/will + 動(dòng)詞原形
If he comes, he will bring his violin.
典型例題
The volleyball match will be put off if it ___.
A.will rain B. rains C. rained D. is rained
答案B。真實(shí)條件句主句為將來(lái)時(shí)，從句用一般現(xiàn)在時(shí)。
注意：
1) 在真實(shí)條件句中，主句不能用be going to表示將來(lái)，該用shall, will.
(錯(cuò)) If you leave now, you are never going to regret it.
(對(duì)) If you leave now, you will never regret it.
2) 表示真理時(shí)，主句謂語(yǔ)動(dòng)詞便不用shall (will) +動(dòng)詞原形，而直接用一般現(xiàn)在時(shí)的動(dòng)詞形式。
16.2 非真實(shí)條件句
1)時(shí)態(tài)：可以表示過去，現(xiàn)在和將來(lái)的情況。它的基本特點(diǎn)是時(shí)態(tài)退后。
a. 同現(xiàn)在事實(shí)相反的假設(shè)。
句型 ： 條件從句主句
一般過去時(shí)should( would) +動(dòng)詞原形
If they were here, they would help you.
b. 表示于過去事實(shí)相反的假設(shè)。
句型： 條件從句 主句
過去完成時(shí) should(would) have+ 過去分詞
If she had worked harder, she would have succeeded.
The rice would not have been burnt if you had been more careful.
If my lawyer had been here last Saturday, he would have prevented me from going.
If he had come yesterday, I should / would have told him about it.
含義：He did not come yesterday, so I did not tell him about it.
If he had not been ill and missed many classes, he would have made greater progress.
含義： He was ill and missed many lessons, so he did not make greater progress.
c. 表示對(duì)將來(lái)的假想
句型： 條件從句 主句
一般過去時(shí) should+ 動(dòng)詞原形
were+ 不定式 would + 動(dòng)詞原形
should+ 動(dòng)詞原形
If you succeeded, everything would be all right.
If you should succeed, everything would be all right.
If you were to succeed, everything would be all right.
16.3 混合條件句
主句與從句的動(dòng)作發(fā)生在不同的時(shí)間，這時(shí)主，從句謂語(yǔ)動(dòng)詞的虛擬語(yǔ)氣形式因時(shí)間不同而不同，這叫做混合條件句。
If you had asked him yesterday, you would k now what to do now.
(從句與過去事實(shí)相反，主句與現(xiàn)在事實(shí)相反。)
If it had rained last night (過去), it would be very cold today (現(xiàn)在).
16.4 虛擬條件句的倒裝
虛擬條件句的從句部分如果含有were, should, 或had, 可將if省略，再把were, should或had 移到從句句首，實(shí)行倒裝。
Were they here now, they could help us.
=If they were here now, they could help us.
Had you come earlier, you would have met him
=If you had come earlier, you would have met him.
Should it rain, the crops would be saved.
=Were it to rain, the crops would be saved.
注意：
在虛擬語(yǔ)氣的從句中，動(dòng)詞’be’的過去時(shí)態(tài)一律用"were"，不用was， 即在從句中be用were代替。
If I were you, I would go to look for him.
如果我是你，就會(huì)去找他。
If he were here, everything would be all right.
如果他在這兒，一切都會(huì)好的。
典型例題
_____ to do the work, I should do it some other day.
A. If were I B. I wereC. Were ID. Was I
答案C. 在虛擬條件狀語(yǔ)中如果有were, should, had這三個(gè)詞，通常將if省略，主語(yǔ)提前, 變成 were, should, had +主語(yǔ)的形式。但要注意，在虛擬條件狀語(yǔ)從句中，省略連詞的倒裝形式的句首不能用動(dòng)詞的縮略形式。如我們可說 Were I not to do., 而不能說 Weren’t I to do.
16.5 特殊的虛擬語(yǔ)氣詞：should
1) It is demanded / necessary / a pity + that…結(jié)構(gòu)中的主語(yǔ)從句的謂語(yǔ)動(dòng)詞要用should 加動(dòng)詞原形， should 可省略。
句型：
(1)suggested
It is (2)importantthat…+ (should) do
(3) a pity
(1)suggested, ordered, proposed, required, demanded, requested, insisted; + (should) do
(2)important, necessary, natural, strange
a pity, a shame, no wonder
(3)It is suggested that we (should) hold a meeting next week.
It is necessary that he (should) come to our meeting tomorrow.
2)在賓語(yǔ)從句中的應(yīng)用
在表示命令、建議、要求等一類動(dòng)詞后面的從句中。
order, suggest, propose, require, demand, request, insist, command, insist + (should) do
I suggest that we (should) hold a meeting next week.
He insisted that he (should ) be sent there.
注意： 如suggest, insist不表示"建議" 或"堅(jiān)持要某人做某事時(shí)"，即它們用于其本意"暗示、表明"、"堅(jiān)持認(rèn)為"時(shí)，賓語(yǔ)從句用陳述語(yǔ)氣。
The guard at gate insisted that everybody obey the rules.
判斷改錯(cuò):
(錯(cuò))You p ale face suggests that you (should) be ill.
(對(duì)) Your pale face suggests that you are ill.
(錯(cuò)) I insisted that you ( should) be wrong.
(對(duì)) I insisted that you were wrong.
3)在表語(yǔ)從句，同位語(yǔ)從句中的應(yīng)用
在suggestion, proposal, idea, plan, order, advice等名詞后面的表語(yǔ)從句、同位語(yǔ)從句中要用虛擬語(yǔ)氣，即(should)+動(dòng)詞原形。
My idea is that we (should) get more people to attend the conference.
I make a proposal that we (should) hold a meeting next week.
16.6 wish的用法
1)用于wish后面的從句，表示與事實(shí)相反的情況，或表示將來(lái)不太可能實(shí)現(xiàn)的愿望。其賓語(yǔ)從句的動(dòng)詞形式為：
真實(shí)狀況wish后
從句動(dòng)作先于主句動(dòng)詞動(dòng)作現(xiàn)在時(shí)過去時(shí)
(be的過去式為 were)
從句動(dòng)作與主句動(dòng)作同時(shí)發(fā)生過去時(shí)過去完成時(shí)
(had + 過去分詞)
將來(lái)不大可能實(shí)現(xiàn)的愿望將來(lái)時(shí)would/could +
動(dòng)詞原形
I wish I were as tall as you.我希望和你一樣高。
He wished he hadn’t said that. 他希望他沒講那樣的話。
I wish it would rain tomorrow. 我希望明天下雨就好了。
2)Wish to do表達(dá)法。
Wish sb / sth to do
I wish to see the manager. = I want to see the manager.
I wish the manager to be informed at once. (= I want the manager to be informed at once.)
16.7 比較if only與only if
only if表示"只有";if only則表示"如果……就好了"。If only也可用于陳述語(yǔ)氣。
I wake up only if the alarm clock rings. 只有鬧鐘響了，我才會(huì)醒。
If only the alarm clock had rung.當(dāng)時(shí)鬧鐘響了，就好了。
If only he comes early.但愿他早點(diǎn)回來(lái)。
16.8 It is (high) time that
It is (high) time that 后面的從句謂語(yǔ)動(dòng)詞要用過去式或用should加動(dòng)詞原形，但should不可省略。
It is time that the children went to bed.
It is high time that the children should go to bed.
16.9 need "不必做"和"本不該做"
didn’t need to do表示： 過去不必做某事, 事實(shí)上也沒做。.
needn’t have done表示： 過去不必做某事, 但事實(shí)上做了。
John went to the station with the car to meet Mary, so she didn’t need to walk back home. 約翰開車去車站接瑪麗，所以她不必步行回家了。
John went to the station with the car to meet Mary, so she needn’t have walked back home. 約翰開車去車站接瑪麗，所以她本不必步行回家了。 (Mary步行回 家，沒有遇上John的車。)
典型例題
There was plenty of time. She ___.
A. mustn’t have hurried B. couldn’t have hurriedC. must not hurry D. needn’t have hurried
答案D。needn’t have done. 意為"本不必"，即已經(jīng)做了某事，而時(shí)實(shí)際上不必要。
Mustn’t have done 用法不正確，對(duì)過去發(fā)生的事情進(jìn)行否定性推斷應(yīng)為couldn’t have done, "不可能已經(jīng)"。 must not do 不可以(用于一般現(xiàn)在時(shí))。
