he must be at home 如何构成反意疑问句

应该改为
isn't he?
请看详细解释
陈述部分有must 的疑问句，疑问部分根据实际情况而定。
He must be a doctor, isn't he?
You must have studied English for three years, haven't you? / didn't you?
He must have finished it yesterday, didn't he?
must在表"推测"时，根据其推测的情况来确定反意疑问句。
He must be there now, isn't he?
It must be going to rain tomorrow, won't it?

当陈述部分must表示“必须”时，疑问部分用mustn't
当陈述部分must表示“有必要”时，疑问部分用needn't
当must表示“一定”“想必”推测意义时，疑问部分不用must,而要根据陈述部分的不定式结构以及含义采用相应的动词形式
例如：You must be hungry,aren't you?

mustn't he?
反意疑问句必须前后一致.若是否定回答,另当别论.如:
Must I be at home?
No, you needn't.

同意楼上的意见。反意疑问句应该是mustn't he?

isn't he?