求教：xdf语法分册上的一道语法题

128. 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 of gasoline or diesel fuel do

C.      less of certain pollutants than gasoline or diesel fuel

D.     fewer of certain pollutants than does burning of gasoline or diesel fuel

E.      less of certain pollutants than those burning of gasoline or diesel fuel

答案选择E，我是理解的，因为有了those指代vehicles，than左右对称，且句意正确。

但不明白的是为什么是less呢？pollutant在这里不是复数么？
        而且查了字典发现pollutant可以是cn或者unc的。

请达人指教，多谢。

把多余的成分去掉，就会发现句子是vehicles emit...than vehicle。只有e中的those 指代了vehicle，使句子中两个进行比较的事物的平衡的。其他句子都是vehicle和燃料的比较

嗯，gmat里面，好像不管单复数只要是事物都用less,碰到人才用few

在这里也许可以解释

好像不应该这么解释吧,我记得LZM里说less of在这里是表示一种程度.