16. --Be careful! There is ___ dog lying on the ground.
--Thanks a lot.
A. a B. an C. the D. /
17. --Why did you come back so early today?
--The English party was _________ until next Friday.
A. put up B. put off C. put out D. put down
18. If there are _______ people driving, there will be ______ air pollution.
A. less; less B. less; fewer C. fewer; fewer D. fewer; less
