在句子中如何使用couldn't,mustn't,can't,needn't?答:couldn't, 通常指做不到或不能做(某事),并非指由于自己的能力所限,语气较婉转: 如: I COULD NOT STAY THAT LONG,,,mustn't, 含有"不被允许"的强制暗意. 如: YOU MUSTN'T GO THERE ALONE.can't, 不能,无法做到... HE CAN'T TRANSLATE THE ENTIRE BOOK INTO ENGLISH IN 2 DAYS.needn...