Don't leave the building unless _____ to do so.
问题描述：
Don't leave the building unless _____ to do so.
A.being told B.you will told C.to be told D.told 为什么不是A,
答
Don't leave the building unless _____ to do so.
可以填I tell you或者you are told
一个主动一个被动,被动中you are可以省略unless后面的用法是怎么样的？unless是连词，是除非，如果不 的意思。unless前的句子应和从句的意思相互对应。