It was at the very beginning _____ Mr. Fox made the decision _____ we should send more fire-fighters there.
The new discovery is of ________.
Once _____ , the machine will keep running.
____ in thought, he almost ran into the car in front him.
— Good morning, can I help you?— I’d like to have this watch _______.
Look at the trouble we’re in. If only we _____ our teacher’s advice. A. had taken B would have taken C. took D. have taken