单项选择题
A.what B.which C.that D.who
All of these alternatives are carbon-based fuels（）molec...
单项选择题All of these alternatives are carbon-based fuels（）molecules are smaller and simpler than those of gasoline.
A.which B.who C.what D.whose
The hydrocarbons they do emit are less likely to（）ozone...
单项选择题The hydrocarbons they do emit are less likely to（）ozone.
A.general B.generation C.generate D.generous
Ethanol is commonly used as a gasoline supplement, but ...
单项选择题Ethanol is commonly used as a gasoline supplement, but it is currently about（）methanol.
A.twice as expensive as B.twice as more expensive as C.as twice more expensive as D.as twice expensive as
