Hardly ___________the door when he rushed into the office out of breath.

Jane told me she would not attend the conference ______.

Not once ________ to Michael that he could one day become a top student in his class.

The child tiptoed quietly to the bird.＿＿＿into the forest when he was about to catch it. 

The research is so designed that once ____ nothing can be done to change it.