must be的用法
问题描述：
must be的用法
答
must be doing:肯定某人正在做某事..He must be doing his homework.他一定在做他的作业
must have been doing:肯定某人一直在做的事..He must have been trying his best to study..他肯定一直都在尽力学习..
must表强烈的肯定，shall不那么强烈，could最弱..表推测的情况一般不用can
答
must be doing sth. She must writing.
答
简单说一下吧..must be doing:肯定某人正在做某事..He must be doing his homework.他一定在做他的作业 must have been doing:肯定某人一直在做的事..He must have been trying his best to study..他肯定一直都在尽...
答
You must be very happy.
你一定很开心
You must be Lucy.
你一定是露西
就是这样套进去