He must be the new english teacher 中的must为什么要加be

He must be the new english teacher 中的must为什么要加be He must be our new English teacher,________?A.mustn't he B.d He must be a teacher,_____? He must be a teacher,___ 2. I think she must be our new teacher, _______? "She must be at least forty ."为什么要在must前加be? 为什么要加ed以及must be done 和must be doing He must be happy! he must ( )here.《be》 The man in blue must be your new English tewacher______ ____ The old man over there must be my new English teather,______ The dentist thought he must be very.