4. Because natural gas is composed mostly of methane, a simple hydrocarbon, vehicles powered by natural gas emit less of certain pollutants than those burning gasoline or diesel fuel. (C-p8-16) 大家看看这个句子,为什么than 后面不需要补出动词 do呢?难道不是省略了emit吗?
10. .In an assessment of the problem faced by rural migrant workers, the question of whether they are better off materially than the urban working poor is irrelevant. (B-p80-25) than后面是不是应该补一个be动词?
22. The mistakes children make in learning to speak tell linguists more about how children learn language than do the correct forms they use. (A-P1-28)这一句呢是什么和什么比较?