Vehicles（）only the simplest of the engine improvements that methanol makes feasible would still contribute to an immediate lessening of urban air pollution.

Henry and Tom（）to the particles at the Trade Union ever...

单项选择题Henry and Tom（）to the particles at the Trade Union every Saturday.

Ethanol is commonly used（）a gasoline supplement.A.forB....

单项选择题Ethanol is commonly used（）a gasoline supplement.

The combustion of larger molecules,（）have multiple carb...

单项选择题The combustion of larger molecules,（）have multiple carbon-carbon bonds involves a more complex series of reactions.