用的是虛擬語(yǔ)氣,省略和倒裝三種語(yǔ)法結(jié)構(gòu).前一句可改為 If he had lived longer.如果他（過(guò)去）能活得更久一點(diǎn)的話,表示與過(guò)去事實(shí)相反的虛擬.因?yàn)閺木渲杏胔ad可以把它提到句首.省略should.可以解釋的再具體些嗎？比如：1.如果前半句原型是If he had lived longer，那你說(shuō)should省略了，這個(gè)should是哪里的呢？原句中并沒(méi)有啊。2.If he had lived longer，這個(gè)為什么不是條件狀語(yǔ)從句呢？給你以下例子If I had listened to our teacher carefully, I would have worked out the math problem yesterday.=Had i listened to ,,,,,If I were you ,I would go there at once.=Were I you, I would,,,.,If it should rain tomorrow, we would stop our sports meeting.=should it rain tomorrow,,,,以上三種和你問(wèn)的一樣。也就是說(shuō)在if的虛擬句中如有had. should 和were就可以把它們提前（即倒裝）省略引導(dǎo)詞if。這是省略。同時(shí)這種情況都是在虛擬句中才能有的，所以這是三種語(yǔ)法的結(jié)合。為什么把had. should 和were提前后需要倒裝呢？ if 引導(dǎo)的虛擬句屬于狀語(yǔ)從句的一種嗎？謝謝你哦是狀語(yǔ)從句，以上那些例子可以變?yōu)榈寡b也可不變。但是根據(jù)英美人習(xí)慣是常變的，那樣比較地道。