单项选择题
A.twice as expensive as
B.as twice expensive as
C.as expensive twice as
D.expensive as twice as
单项选择题 Ethanol and methanol have important advantages（）other carbon-based alternative fuels.
单项选择题 On the other hand, alternative fuels do have（）.
单项选择题 There is a growing realization that the only（）way to achieve further reductions in vehicle emissions is to replace conventional diesel fuel and gasoline with cleaner-burning fuels.