He can't be at home.为什么can't后要加be?

He can't be at home.为什么在at前面有be?什么情况下要加Be? Tom _______(can’t/mustn't) be at home .he said he would go t 关于He can't be at home,isn't he?此句是否为反义疑问句? he can't be at home与he may not be at home有什么不同?跪拜请求指点迷津. can't be at home可以转换成can't stay at home吗 He can't be at home.He went to the cinema.合并成一句话 Bob must be at home,________?A.mustn't he B.can't he C.isn't Simon _____ be at home .He is on the playground.A.can't B.mu There can't be anyone at home,___? He can't be home now, for I saw him you mustn't be home at half past ten这句中的be是什么意思,可否不加?I can't can't be用法