16. Because natural gas is composed mostly of methane, a simple hydrocarbon, vehicles powered by natural gas emit less of certain pollutants than the burning of gasoline or diesel fuel.
(A) less of certain pollutants than the burning of gasoline or diesel fuel (B) fewer of certain pollutants than burning gaso- line or diesel fuel do (C) less of certain pollutants than gasoline or diesel fuel (D) fewer of certain pollutants than does burning gasoline or diesel fuel (E) less of certain pollutants than those burning gasoline or diesel fuel
答案是E。pollutants是可数名词，应该是fewer吧。 emit应该和do对应起来吧 我怎么觉得是B。觉得白勇里面讲过，可是pdf居然不能搜索。 | 
