看两个例子,帮我总结一下must be的用法!
1.He must be home before six o'clock.
He has to be home before six o'clock.
2.He must be tired.
I think he is probably tired.
这是课后练习中的题目要求,要求模仿例句改写以下句子：
He must be here at six o'clock.
He has to be here at six o'clock.
He must be busy.
I think he is probably busy.
句中的must be应该是“一定”的意思吧,为什么有的改写成have to ,有的改写成probably?