這個(gè)要分兩種情況：
1、must表示“必須,一定”,反意問句用must,如：
You must do it today,mustn't you?
You mustn't do that again,must you?
2.must表示“一定,肯定”推測(cè)的時(shí)候,和二樓說的一樣.要根據(jù)情況來定.
如：You must be hungry now ,aren't you?對(duì)現(xiàn)在的情況進(jìn)行推測(cè),用一般現(xiàn)在時(shí).
You must have finished your homework,didn't you?對(duì)過去的情況進(jìn)行推測(cè),用一般過去時(shí).
You must have studied English for three years,haven't you?表示推測(cè)的情況有一段的時(shí)間狀語,反意部分要用現(xiàn)在完成時(shí).