impossible和couldn't的差别和用法It_____________（不可能）be him！为什么要用couldn't不能用impossible？

impossible和couldn't的差别和用法It_____________（不可能）be him！为什么要用couldn't不能用impossible？ couldn't have done和couldn't do的区别 didn't 和couldn't的区别, could和couldn't的不同 couldn`t的意思和时态 couldn t和 I couldn't bear it 和I couldn't bear this的区别 couldn't和shouldn't的区别,急要 could和 must和 couldn't 的区别和用法? couldn't get through.中through的意思,和词性. improbable和impossible的区别 can't和couldn't区别? couldn't的完全形式 couldn't与can't的区别! can't与couldn't的区别 couldn't have finished和 can't have finished 的区别 couldn't的完整形式是什么 words I couldn't say 的伴奏