托福语法学习：条件句类型3

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　if从句中的动词用过去完成时，主句中的动词用条件完成时。这种句子所指的时间是过去；所提出的条件是不可能实现的，因为if从句中的动作在过去并未发生。
  c% h) s8 c7 l# s0 ]7 b　　If I had known that you were coming I would have met you at the air－port．
7 \3 O8 @& [- ~; ]　　要是我早知道你要来的话，我就会在机场接你了。（但我不知道，所以我也没去。）
　　If he had tried to leave the country he would have been stopped at the frontier．
　　要是他当时试图离开这个国家，他就会在边界被阻拦。（但他并未这样做。）
　　基本形式可能的变化形式
( `( M: Z; m$ I1 G: S3 ?2 P2 B　　1 可以用could或might而不用would：
　　If we had found him earlier we could have saved his life．
+ J2 x8 ~* l. }　　要是我们那时早点找到他的话，我们会把他救活的。（能力）
　　If we had found him earlier we might have saved his life．
# t. i% U$ s: e6 m5 G" [　　要是我们那时早点找到他的话，我们可能会把他救活的。（可能性）
' ?# e* ^( n; i( i7 t  ?# r　　If our documents had been in order we could have left at once．
　　要是我们的证明文件都齐备的话，我们那时就能够马上走。（能力或允许）
　　2 可以用条件完成进行时：
$ Q/ X- @1 _9 d. @$ Z1 m　　At the time of the accident I was sitting in the back of the car，because Tom’s little boy was sitting beside him in front．If Tom’s boy had not been there I would have been sitting in front．
) o+ ~0 P/ ~) n# J　　事故发生的时候，我坐在车子的后座，因为汤姆的小儿子坐在前边他的身旁。要是汤姆的孩子没坐在那里的话，我就会坐在前面了。
　　3 可以在if从句中用过去完成进行时：
　　I was wearing a seat belt．If I hadn’t been wearing one I’d have been seriously injured．
　　我当时系了安全带。要是没有系上的话，我就会受重伤了。
" ~4 ~7 g& H8 y9 b2 V; r3 n　　4 可以把类型2和类型3结合起来：
% h) k4 @4 B2 F; n/ C0 @2 _) S　　The plane I intended to catch crashed and everyone was killed．If I had caught that plane I would be dead now／I would have been killed．
　　我原想赶乘的那架飞机坠毁了，所有乘客都遇难身亡。要是我赶上了那架飞机，我也就没命了／我就会摔死了。（类型 3）
　　If I had worked harder at school I would be sitting in a comfortable office now；I wouldn’t be sweeping the streets．
　　要是在上学时学习再努力一些，我现在就会坐在舒适的办公室里，而
7 z) s& e' y2 T( n: d# n8 S4 U　　不会是在扫大街了。（但我上学时不努力，因而我现在在扫大街。）
　　5 had可以位于句首并省略if：
' \7 Q/ @- l8 E- P/ y　　If you had obeyed orders this disaster would not have happened．相当于：
　　Had you obeyed orders this disaster would not have happened．
8 c+ Q7 G! |3 v  \　　要是你当时服从了命令，这场灾难就不会发生了。