He is at least as tall as his brother, if not _________.
The professor managed to find some grounds (facts)_________his arguments.
I would like a job which pays more,but _______I enjoy the work I’m doing at the moment.
----- Have you ______ some new ideas? ------ Yeah.I’ll tell you later.
Leave your key with a neighbor ______you lock yourself out one day.
A new_____ bus service to Tianjin Airport started to operate two months ago.