done的虚拟结构，条件句中有had且省略if时，要将had提到主语之前。

　　8. If I ________ (learn) my lessons hard, I wouldn't have failed in the final exam.

　　答案：had learned　根据主句中的"wouldn't have failed"可知，从句叙述过去的情况，故用过去完成时。

　　9. Look at the trouble we're in. If only we ________ (take) our teacher's advice!

　　答案：had taken　后一句句意：要是我听从了老师的建议多好！表示与过去情况相反的虚拟，用过去完成时。

　　10. -How I wish I had studied harder when I was in senior school!

　　-If you had, you ________ (be) a university student now.

　　答案：would/could/might/should be　句意：--我多么希望在高中的时候学习能再努力点啊！--如果你努力点学习，现在你就是一个大学生了。本题中从句是对过去的虚拟，主句中有时间状语now，是对现在的虚拟，所以用"would/could/should/might＋动词原形"的形式。

　　[提升·实战能力]

　　Ⅴ. 完形填空

I spoke to a group of young people not long ago. When I finished, they ___1___ me to go out with them to have a good time. When I was at their ___2___， I probably would have given in to that