单项选择题
The combustion of larger molecules,（）have multiple carbon-carbon bonds involves a more complex series of reactions.
A.what B.which C.that D.who
单项选择题 All of these alternatives are carbon-based fuels（）molecules are smaller and simpler than those of gasoline.
单项选择题 The hydrocarbons they do emit are less likely to（）ozone.
单项选择题 Ethanol is commonly used as a gasoline supplement, but it is currently about（）methanol.
