题目选项分析

Ethanol is a derivative of corn and other grains. When burned as fuel, it emits significantly lower levels of carbon monoxide, a major atmospheric pollutant, than does gasoline. For that reason, environmentalists claim that ethanol is a better source of energy than gasoline.

Which of the following, if true, most strongly supports the environmentalists' claim?

【选项】When burned as fuel, ethanol does not release any pollutants at higher levels than does gasoline.