should have done,must have done都表示該做的沒做,是虛擬語氣,用于表達與過去的事實相反.但should have done語氣上沒有must have done重.它們有細微的差別.給你2個句子比較一下:
1)You should not have told him such a bad news when he was ill.
2)You mustn't have told him such a bad news when he was ill.
這2句話翻譯過來可以是一樣的,但是第1句的含義是,雖然你這么做錯了,但是說話者并沒有責怪你,責備你的意思,只是叫你注意,以后可不能這么做了.
而第2句話就可以是在責備你為什么要這么做,設想,如果說話者本來平時就和你關系不太好,第2句話甚至可以可以讓你難堪,下不了臺,對你進行報復.
總之,細微的差別就在語氣之中.虛擬語氣是英語學習的重難點,多加油哦!