Unless _____ to speak, you should remain silent at the conference [ ]

My life has been _____ with many milestones and accomplishments of which I am proud.

It was not until I came here ________I realized this place was famous for not only its beauty but also its weather. (2012·湖南，30)

Ia bank account after I made﹩1 000 by doing a part-time job during the summer vacation

_____ your letter, I would have written back two days ago. [ ]