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 gasoline 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 选e,agree,但pollutants怎么用less呢?
20. Byron possessed powers of observation that would have made him a great anthropologist and that makes his letters as a group the rival of the best novels of the time. (A) makes his letters as a group the rival of (B) makes his letters as a group one to rival (C) makes his letters a group rivaling (D) make his letters as a group the rival of (E) make his letters a group which is the rival of 选d,我选e,为什么不是make sth. sth.呢?为什么要用as?