1.條件句中的虛擬語(yǔ)氣類(lèi)型
(1)將來(lái)時(shí)的條件句中的虛擬語(yǔ)氣。如：
If it were to rain tomorrow, the meeting would be put off.
(2)現(xiàn)在時(shí)的條件句中的虛擬語(yǔ)氣。如：
If he studied at this school, he would know you well.
(3)過(guò)去時(shí)的條件句中的虛擬語(yǔ)氣。如：
I could have done better if I had been more careful．

2.運(yùn)用條件句中的虛擬語(yǔ)氣時(shí)，須注意的幾個(gè)問(wèn)題
(1)當(dāng)從句的主語(yǔ)為第三人稱(chēng)單數(shù)時(shí)，謂語(yǔ)動(dòng)詞若是系動(dòng)詞be時(shí)，可用was代替were。但在倒裝虛擬結(jié)構(gòu)及if I were you, as it were中，只能用were。如：Were I ten years younger, I would study abroad.

(2)當(dāng)條件狀語(yǔ)從句表示的行為和主句表示的行為所發(fā)生的時(shí)間不一致時(shí)，動(dòng)詞的形式要依據(jù)它所表示的時(shí)間來(lái)調(diào)整。
①?gòu)木涞膭?dòng)作與過(guò)去事實(shí)相反，而主句的動(dòng)作與現(xiàn)在或現(xiàn)在正在發(fā)生的事實(shí)不符。如：
If I had worked hard at school, I would be a teacher, too.
If they had informed us, we would not come here now.
②從句的動(dòng)作與現(xiàn)在事實(shí)相反，而主句的動(dòng)作與過(guò)去事實(shí)不符。如：
If he were free today, we would have sent him to Beijing.
③從句的動(dòng)作與過(guò)去發(fā)生的情況相反，而主句的動(dòng)作與現(xiàn)在正在發(fā)生的情況相反。如：
If it had not been raining too much, the crops would be growing much better.

(3)當(dāng)虛擬條件句的謂語(yǔ)動(dòng)詞含有were, should, had時(shí)，if可省略，而將were, should, had等詞置于句首。如：
Should he agree to go there, we would send him there.
Were she here, she would agree with us.
Had he learnt about computers, we would have hired him to work here.

(4)有時(shí)，句子沒(méi)有直接給出假設(shè)情況的條件，而須通過(guò)上下文或其他方式來(lái)判斷。如：
I would have come to see you, but I was too busy.
But for his help, we would be working now.
Without your instruction, I would not have made such great progress.

(5)有時(shí)，虛擬條件句中，主、從句可以省略其中的一個(gè)，來(lái)表示說(shuō)話(huà)人的一種強(qiáng)烈的感情。
①省略從句
He would have finished it.
You could have passed this exam.
②省略主句
If I were at home now.
If only I had got it.