All those second-hand cars are sold at                  before

 I think it _____ that she should be knowledgeable about computers for her present job.

There is gas _______ somewhere; can you smell it?

As the quality of the city’s air continues to give rise to ______, the residents are encouraged to set off fewer fireworks. 

—Nowadays children have more freedom.—I agree. They ________ do what they like.