是这样的,needn't do 和 don't need to do 两者有些差别.就像needn't have done 和 didn't need to do 一样.从用法上,前者是情态动词,后者是实义动词.从意义上,前者暗示已经做了,有“本不需要”的意思,后者暗示还没...