Which of the following, if true, provides

问题：

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