题目

There is no point advocating banning smoking in public________ the law is introduced. A．when  B．unless  C．since  D．because 答案：B　[考查状语从句。句意：在公共场合提倡禁烟没有任何意义，除非可以提交讨论相关法规。unless“除非”，符合句意。]

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