句型31
(從句)If + were/did(動(dòng)詞的過去式)，(主句)主語 + would/might/should/could + do(表示對(duì)現(xiàn)在情況的假設(shè))
[例句]
If I were you, I would not be so proud. 如果我是你，我不會(huì)如此自負(fù)。
I don't have a cellphone. If I had one, it would be convenient for me to get in touch with others.
If I were in your position, I would think better of it. 如果我處在你的位置，我會(huì)好好考慮它。

句型32
(從句)If + had done, (主句)主語+ would/might/should/could +have done(表示對(duì)過去或已經(jīng)發(fā)生事情的虛擬假設(shè))
[例句]
What a pity it is that you didn't attend the concert yesterday! If you had attended the concert, you would have seen the famous singer.
真遺憾昨天你沒有去聽音樂會(huì)。如果你去了，就能見到那位著名歌手。
Anyone in his position would have done the same.
=If anyone had been in his position, he would have done the same. 任何處在他位置的人都會(huì)這樣做的。

句型33
(從句)If + were/did(動(dòng)詞過去式)/were to do/should do，(主句)主語+ would/might/should/could + do(表示對(duì)將來的假設(shè))
[例句]
If he should refuse (= If he were to refuse=If he refused), it didn't matter at all. 萬一他拒絕了，那也沒關(guān)系。
If you shouldn't pass the college entrance examination, what would you do?
萬一高考不中，你該怎么辦?

句型34
虛擬語氣條件句的倒裝
在虛擬條件句中，如果出現(xiàn)有were, had, should，可以省去if, 把這些詞放在句子前面，構(gòu)成虛擬倒裝句。
[例句]
Should he act like that again, he would be fined. 如果他還這樣做，就要受罰。
Had the doctor come in time last night (=If the doctor had come in time last time), the boy would have been saved. 昨天晚上要是醫(yī)生及時(shí)到達(dá)，小孩就會(huì)得救。
Were I to go to the moon one day, I would see it with my own eyes.
Had I enough money (= If I had enough money), I would buy a larger house.

句型35
if only引起的感嘆句，相當(dāng)于 "How I wish + 賓語從句"，意思是"但愿……;要是……就好了"
[例句]
If only he could come! 他要是能來就好了!
If only we students didn't have so much homework!要是沒有這么多的作業(yè)該多好!
If only I hadn't been so careless in the exam! 我當(dāng)時(shí)沒有那么粗心就好了!

句型36
if it were not for… (= were it not for…)
if it hadn't been for… (= had it not been for…)"要不是因?yàn)橛小?如果不是……"
[注意]這種結(jié)構(gòu)中不能用否定結(jié)構(gòu)的縮寫形式，即不能用weren't it for…)
[例句]
If it hadn't been for (= Had it not been for) the determined captain, all the passengers on board wouldn't have been saved. 要不是船長(zhǎng)一直堅(jiān)強(qiáng)，船上的旅客就不會(huì)得救。
If it were not for your rich parents, you couldn't live so easy a life. 要不是你父母有錢，你的生活不會(huì)如此安逸。
If it were not for the expense, I would go abroad now. 如果不是因?yàn)榻?jīng)費(fèi)問題，我現(xiàn)在就出國(guó)了。

句型37
"but for + 名詞"和"but that +從句"，意思是"倘若不是;要不是"，接虛擬語氣
[例句]
But for air and water, nothing could live. (= If there were no air or water, nothing could live.)
如果沒有空氣和水，什么東西都難以生存。
But for the storm, we should have arrived earlier.
= If it hadn't been for the storm, we should have arrived earlier. 如果不是暴風(fēng)雨，我們?cè)缇偷搅恕?br> But for you, we couldn't have carried out the plan. 要不是你的話，我們無法實(shí)施那項(xiàng)計(jì)劃。
She could not have believed it but that she saw it. 若非親眼所見，她是不會(huì)相信的。

句型38
在動(dòng)詞insist(1堅(jiān)持做某事)，order, command(2命令), advise, suggest, propose(3建議做某事)，demand, require, request, ask(4要求)等表示建議、命令、要求的名詞性從句中謂語動(dòng)詞要用虛擬語氣?；揪湫停褐髡Z+ (should) + 動(dòng)詞原形。另外像decide, desire, intend, recommend等也要接(should)+動(dòng)詞原形結(jié)構(gòu)。
[例句]
Mother insists that Tom (should) go to bed at nine o'clock.(賓語從句)
We suggested that the meeting (should) be held at once.
It was required that the crops (should) be harvested at once.(主語從句)
The suggestion that he (should) be invited was rejected.(同位語從句)
That is their demand that their wages (should) be increased.(表語從句)
[注意1]
advice, suggestion, order, demand, proposal, request, desire, command, decision, requirement等名詞引導(dǎo)的同位語從句或表語從句，謂語動(dòng)詞用 (should) + 動(dòng)詞原形。
[注意2]
It's suggested/ advised/ demanded/ordered/requested/proposed/required/desired等結(jié)構(gòu)后的主語從句中，謂語動(dòng)詞用(should) + 動(dòng)詞原形。
[注意3]suggest意思是"表明，暗示;說明"時(shí);insist意思是"堅(jiān)持觀點(diǎn)，堅(jiān)持看法"時(shí)，句子不能用虛擬語氣。
[例句]
He insisted that he was innocent.=He insisted on his innocence. 他堅(jiān)持說自己是無辜的。
He insisted that he had never done wrong. 他堅(jiān)持說沒有做錯(cuò)事情。
Are you suggesting that I'm not suited for the job? 你是在暗示說我不適合做那項(xiàng)工作?
The look on his face suggested that the teacher was quite satisfied with the result. 臉上的表情說明老師對(duì)結(jié)果感到滿意。

句型39
It is necessary/important/natural/impossible/essential(基本的)等結(jié)構(gòu)后的主語從句中要用虛擬語氣，即主語+(should)+動(dòng)詞原形
[例句]
It's necessary that Tom take the exam first. Tom有必要先參加考試。
With the society developing very fast, it's quite necessary/important that we (should) have a good knowledge of English and computer. 隨著社會(huì)的快速發(fā)展，我們有必要精通英語和電腦。

句型40
It's strange/surprising/a pity/a shame/a surprise (that) … should do…should表示"竟然"
[例句]
It's a pity that she should miss the chance. 很遺憾她錯(cuò)過了機(jī)會(huì)。
It's really surprising that a prophecy(預(yù)言)should coincide with the fact so exactly. 令人驚訝的是，預(yù)言和事實(shí)竟然如此巧合。
It's strange that he shouldn't pass the exam. 奇怪的是他竟然沒有通過考試。