问题补充：
If there are people driving, there will be air pollution.
A. more; less
B. less; fewer
C. fewer; more
D. fewer; less
答案：
A. more; less
B. less; fewer
C. fewer; more
(答案→)D. fewer; less
解析：more更多的,可修饰可数名词复数与不可数名词;less更少的,修饰不可数名词;fewer更少的,修饰可数名词复数.句意:如果开车的人们更少,空气污染就会更少.前文people是可数名词,下文空气污染是抽象名词,不可数,故选D.
