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

A invited         B inviting           C being invited    D having invited

 Young people tend to get up very late unless ________ to rise early.

    A. required       B. requiring         C. they were required  D. to require

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

．_________we are allowed- , we can’t drink any beer.

         A．As long as; to do                  B．Unless; to

         C．Until; doing                  D．On condition that; doing so

________ we are allowed ________ , we can’t drink any beer.

A. As long as; to do                    B. If; to

C. Unless; to                           D. On condition that; doing so