Leave your key with your neighbor ________ you lock yourself out one day.(2012·辽宁)
The computer, _______ he paid ¥3,000, was once owned by his uncle.
In the past we lost many chances, _______ we paid little attention.
The pen, _______ I had been writing for ten years, was broken.
Mary has two brothers, ________ are doctors.
The problem _______ you argued about yesterday has been solved.