"She must be at least forty ."为什么要在must前加be?

"She must be at least forty ."为什么要在must前加be? She must be at least forty.请问其中的at least是副词,还是介词短语,用来修饰哪个词? 连词成句 1.must she forty least be at 2.not he is than more twen She is at least five years old 和She must be at least five ye she must be at least thirty five years old.in ma opinion she She must be at least thirty-five years old.In my opinion she 用must或can't填空 1、that woman ( ) be at least 50.she looks old I think she must be over forty.有语法错误吗 over must forty be she连词成句 ipod touch password must be at least 8 characters you must be at least tevel 19 to enter He must be the new english teacher 中的must为什么要加be