表示与过去事实相反的情况 从句:If 主语+had+done 主句:主语+should/would/could/might+have done eg: 1. If I had gotten there earlier,I should/could have met her. 如果我早到那儿,我就会见到她。 (事实:去晚了) 2.If he had taken my advice,he would not have made such a mistake. 如果他听我的劝告的话,就不会犯这样的错误了。 (事实:没有听我的话)