類別

用法

例句

If引導(dǎo)的條件從句

與現(xiàn)在事實(shí)相反

從句動(dòng)詞：過(guò)去式（be用were）

主句動(dòng)詞：should/would/could/might+動(dòng)詞原形

If he were here, he would help us.

與過(guò)去事實(shí)相反

從句動(dòng)詞：had+過(guò)去分詞

主句動(dòng)詞：should/would/could/might+have+過(guò)去分詞

If I had been free, I would have visited you.

與將來(lái)事實(shí)相反

從句動(dòng)詞：過(guò)去式/ should+動(dòng)詞原形/ were+不定式

主句動(dòng)詞：should/would/could/might+動(dòng)詞原形

If it should rain tomorrow, we would not go camping.

其它狀語(yǔ)從句

as if引導(dǎo)的狀語(yǔ)從句中動(dòng)詞用過(guò)去式或過(guò)去完成式

They are talking as if they had been friends for years.

in order that / so that引導(dǎo)的狀語(yǔ)從句中動(dòng)詞用can / could / may / might / would等+動(dòng)詞原形

Turn on the light so that we can see it clearly.

賓語(yǔ)從句

demand, suggest, order, insist后接的從句中動(dòng)詞為should+動(dòng)詞原形

He suggested that we not change our mind.

wish后的從句中分別用過(guò)去式，過(guò)去完成式和should/would+動(dòng)詞原形表示與現(xiàn)在，過(guò)去和將來(lái)情況相反

I wish I could be a pop singer.

主語(yǔ)從句

在It is necessary / important / strange that…, It is suggested / demanded / ordered / requested that…等從句中，謂語(yǔ)動(dòng)詞用should+動(dòng)詞原形

It is strange that such a person should be our friends.

其它句型中

It is time that…句型中動(dòng)詞用過(guò)去式或should+動(dòng)詞原形

It’s high time that we left.

would rather所接的從句中動(dòng)詞用過(guò)去式或者過(guò)去完成式

I would rather you stayed at home now.

If only句型中動(dòng)詞常用過(guò)去式或者過(guò)去完成式，表示強(qiáng)烈的愿望

If only our dream had come true!

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相關(guān)閱讀：高中英語(yǔ)必修：動(dòng)詞的分類及基本形式