must＋have done 句型
must＋have done 表对过去发生事情有把握推测.
但是可不可以用must +be 这样的句子来表示?
比如说 He must have made it for you.可以变成 He must be made it for you
另外 疑问否定中的can't/couldn't have done .什么时候用can't 什么时候用couldn't