We complained to the travel agency about the horrible service during our trip，but no one has________by now.

No student ________ go out of the school campus after 10：00 at night without permission according to the school regulations.

You can’t ______ a hat in class.

Excuse me, I don’t think you can smoke here.—Really sorry. I ______ this is a non-smoking room.

The doctor did what he could_________ the dying man.