Question

samanthas urban community is blanketed with smog. which statement best explains the reason for this poor air quality?
people crowd sidewalks as they walk to shopping malls.
people use underground subways for long - distance travel.
people ride bicycles to commute to work on a daily basis.
people drive cars whenever they need to go somewhere.

Explanation:

汽车尾气是城市雾霾（smog）的重要来源。步行去购物中心、乘坐地铁、骑自行车都不会产生大量污染空气的尾气。而人们无论何时出行都开车，汽车尾气排放会导致空气质量变差，形成雾霾。

Answer:

People drive cars whenever they need to go somewhere.