英语选择题　hemusthavefinishedhishomew
　he must have finish his homework fora long time,hasn't he? hasn't 能不能用ｎｅｅｄｎ＇ｔ替换
当然不可以了 must have done--- 对发生在过去但对现在造成影响的动作进行推测，用haven't/hasn't must have done 对过去的某一时间的事情猜测 ， 用didn't He must have read the novel yesterday,didn't he?