Something must be done to prevent factories ________ poisonous gases so as to keep the city ________.
I failed in the last exam and only then __________ the importance of studies.
—Will you go to Tom’s birthday party tomorrow? —No,________invited to, for she is the last person I’d like to see.
Most people are familiar with the idea that all matter in the universe ________ atoms.
After a day’s hard work, I went back home ________.
_____ its low price, the advantage of this car lies in its good quality.