4. if條件句中的虛擬語(yǔ)氣形式
1）if 非真實(shí)條件句所表示的假設(shè)則是不可能或不大可能發(fā)生或?qū)崿F(xiàn)的，句中的主句與從句都用虛擬語(yǔ)氣。
在if非真實(shí)虛擬條件句中，主句和從句謂語(yǔ)動(dòng)詞主要有下面幾種形式：
假設(shè)類(lèi)型 條件從句謂語(yǔ)動(dòng)詞形式 主句謂語(yǔ)動(dòng)詞形式
與現(xiàn)在事實(shí)相反 動(dòng)詞過(guò)去時(shí)（be 用 were） should（would，could，might） + 動(dòng)詞原形
與過(guò)去事實(shí)相反 had + 過(guò)去分詞 should（would，could, might）+ have + 過(guò)去分詞
與將來(lái)事實(shí)可能相反 動(dòng)詞過(guò)去時(shí)（should+動(dòng)詞原形，were to + 動(dòng)詞原形） should（would，could，might）+ 動(dòng)詞原形
if there were no gravity, we should not be able to walk.
假如沒(méi)有引力，我們就不可能行走。
i wouldn’t have known what these were for if i hadn’t been told.
假如別人不告訴我，我就不知道這些東西是干什么的了。
2） 正式文體中，有時(shí)可把虛擬條件句中的連詞if省去，而將were，had, should等助動(dòng)詞（不包括行為動(dòng)詞）提到主語(yǔ)前面。如果句中沒(méi)有were，had或should時(shí)，既不能省略if，也不能倒裝。例如：
were i to meet him tomorrow (= if i were to met him tomorrow), i should ask him about it.
要是我明天見(jiàn)到他，我就會(huì)問(wèn)他這件事的。
had i had the money last year (= if i had had the money last year), i would have bought the house.
如果我去年有了這筆錢(qián)，我就買(mǎi)那所房子了。
should there be any trouble with the boiler, the automatic controlling unit would cut off the fuel oil supply.
假如鍋爐出問(wèn)題的話，自控裝置會(huì)自動(dòng)切斷燃油的供給。
3） 通常情況下，在非真實(shí)條件句中主句和從句的謂語(yǔ)動(dòng)詞所指時(shí)間是一致的，但有時(shí)也可能指不同的時(shí)間，這時(shí)要根據(jù)上下文的意思采用不同的謂語(yǔ)動(dòng)詞形式。例如：
if i were you, i would have taken his advice.
我要是你，我就采納了他的建議。（從句指現(xiàn)在，主句指過(guò)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(huì)長(zhǎng)得更好。（從句指過(guò)去，主句指現(xiàn)在）
1）if 非真實(shí)條件句所表示的假設(shè)則是不可能或不大可能發(fā)生或?qū)崿F(xiàn)的，句中的主句與從句都用虛擬語(yǔ)氣。
在if非真實(shí)虛擬條件句中，主句和從句謂語(yǔ)動(dòng)詞主要有下面幾種形式：
假設(shè)類(lèi)型 條件從句謂語(yǔ)動(dòng)詞形式 主句謂語(yǔ)動(dòng)詞形式
與現(xiàn)在事實(shí)相反 動(dòng)詞過(guò)去時(shí)（be 用 were） should（would，could，might） + 動(dòng)詞原形
與過(guò)去事實(shí)相反 had + 過(guò)去分詞 should（would，could, might）+ have + 過(guò)去分詞
與將來(lái)事實(shí)可能相反 動(dòng)詞過(guò)去時(shí)（should+動(dòng)詞原形，were to + 動(dòng)詞原形） should（would，could，might）+ 動(dòng)詞原形
if there were no gravity, we should not be able to walk.
假如沒(méi)有引力，我們就不可能行走。
i wouldn’t have known what these were for if i hadn’t been told.
假如別人不告訴我，我就不知道這些東西是干什么的了。
2） 正式文體中，有時(shí)可把虛擬條件句中的連詞if省去，而將were，had, should等助動(dòng)詞（不包括行為動(dòng)詞）提到主語(yǔ)前面。如果句中沒(méi)有were，had或should時(shí)，既不能省略if，也不能倒裝。例如：
were i to meet him tomorrow (= if i were to met him tomorrow), i should ask him about it.
要是我明天見(jiàn)到他，我就會(huì)問(wèn)他這件事的。
had i had the money last year (= if i had had the money last year), i would have bought the house.
如果我去年有了這筆錢(qián)，我就買(mǎi)那所房子了。
should there be any trouble with the boiler, the automatic controlling unit would cut off the fuel oil supply.
假如鍋爐出問(wèn)題的話，自控裝置會(huì)自動(dòng)切斷燃油的供給。
3） 通常情況下，在非真實(shí)條件句中主句和從句的謂語(yǔ)動(dòng)詞所指時(shí)間是一致的，但有時(shí)也可能指不同的時(shí)間，這時(shí)要根據(jù)上下文的意思采用不同的謂語(yǔ)動(dòng)詞形式。例如：
if i were you, i would have taken his advice.
我要是你，我就采納了他的建議。（從句指現(xiàn)在，主句指過(guò)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(huì)長(zhǎng)得更好。（從句指過(guò)去，主句指現(xiàn)在）