Unless to speak, you should remain silent at the conference.A invitedB invitingC being in

发布时间：2020-08-15 02:13:41

Unless      to speak,  you should remain silent at the conference.
A invited        B inviting          C being invited   D having invited

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解析：本题考查动词的-ed形式。You 与invite 之间构成被动关系，故用过去分词。Unless invited to speak = Unless you are invited to speak. 答案为A。
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