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：

这句话的意思是“如果不邀请你讲话，你就应该在会议上保持沉默。”相当于unless you are invited to speak, you should remain silent at the conference。从句中的主语与主句中的主语一致，可省略从句中的主语和be动词，因此本句省略了you are。