Which of the following, if true, provides the most logical completion of the passage below
Cars fueled by methanol have a much lower level of emissions of pollutants such as carbon monoxide and environmentally harmful hydrocarbons than gasoline-fueled cars do. Methanol fuel does produce somewhat higher formaldehyde emissions than gasoline does. Nevertheless, a methanol-powered car actually produces less atmospheric formaldehyde pollution than a comparable gasoline-powered car, because （）.
A．compared to carbon monoxide and some hydrocarbons produced by gasoline-powered cars, formaldehyde pollution is not a serious threat to the environment
B．the technical difficulties involved in mass producing methanol-powered cars will prevent them from seriously competing with gasoline-powered cars for several years
C．gasoline-powered cars are required by United States law to be equipped with catalytic converters that reduce emissions of many pollutants
D．measuring a car’s emissions is generally an accurate method of assessing that car’s contribution to atmospheric pollution
E．most formaldehyde pollution generated by gasoline-powered cars results from the photochemical conversion of hydrocarbon emissions into formaldehyde in the atmosphere
参考答案：E
解析：
本题是要找一个选项对以甲醇为燃料的汽车排放出的甲醛比燃烧汽油的汽车排放的甲醛多而污染却少做出合理的解释。(E)指出虽然燃烧汽油本身放出的甲醛不多，但是燃烧汽油所释放的其他碳氢化合物在大气中能发生光化学反应而生成甲醛，因此，燃烧汽油的汽车的实际甲醛排放量应为直接排放量加上间接排放量，这两部分之和有可能大于燃烧甲醇的汽车排放的甲醛。由以上分析可知(E)正确。