单选题

The text suggests which of the following about air pollution?

A Further attempts to reduce emissions from gasoline-fueled vehicles will not help lower urban air-pollution levels.

B Attempts to reduce the pollutants that an individual gasoline-fueled vehicle emits have been largely unsuccessful.

C Few serious attempts have been made to reduce the amount of pollutants emitted by gasoline-fueled vehicles.

D Pollutants emitted by gasoline-fueled vehicles are not the most critical source of urban air pollution.

解析：
推断题。文章首段第一句即指出“尽管单个机动车辆的有毒排放物已大幅减少，但总的车辆数却在稳步增加”，最后一句又指出“人们已经意识到实现车辆废气减少而又不必大规模减少私家车辆的唯一途径是用清洁燃料来代替传统的柴油和汽油燃料”。由此可知，文章要表达的意思是：进一步减少汽油机动车辆的排放物已经不足以降低城市空气污染水平了。A项正确。