Question

Unless ________ to speak, you should remain silent at the conference．

[　　]

A．

invited

B．

inviting

C．

being invited

D．

having invited

Answer 1

答案：A
解析：

主句主语与invite具有被动关系,故此处应使用表被动关系的过去分词invited。unless invited to speak相当于unless you are invited to speak。