must be和must have been 在句子中作什么成份及其时态?

must be和must have been 在句子中作什么成份及其时态? must be和must have been有什么区别 在英语里coms been、must been和may been和come have been、must have be must have been done/must be done 英语中,must have been 和 must have +过去分词,有什么区别 must be和must have be有什么区别 模仿例句改写句子.Example:He must be in the office.→He must have been must be的用法和must have been的用法是什么? there be 中there 什么词性,在句子中作什么词是什么成份, must be,must和have be,have的区别 be,must be,can't have been,must have been吗 she must have been a temporary worker 是什么时态?