32. Which is considered a weakness of the city-level measures to tackle dirty air?

答案：D. They put too much burden on individual motorists.

考点：细节题

粉笔解析：由题干关键词weakness of the city-level measures定位至第三段。该段第二句提到：它们不可避免地把清洁空气的成本推给了个别司机——他们必须支付费用或购买更好的车辆。对比选项，D选项的它们给每个开车的人增加了太多的负担与原文意思一致，故本题答案为D。