should/must/would/could/might/may have done的问题!这些词组里到底哪些是表示推测.哪些是虚拟语气啊?晕了.还有就是could和can什么关系（区别）?might和may什么关系?

must have done 表示推测
might,should ,can ,may have done表示虚拟
could ,might 比can ,may 更不靠谱，

should have done表示“本应该……”,是虚拟must have done表示“一定已经做过……”,是对过去的推测would have done应该是虚拟结构could have done是“本可以……”,是虚拟might/may have done是推测could可以只表...