求助一道语法题 有一道语法题的答案是：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.请问为什么要在比较结构中省略助动词do.白勇说比较结构中be动词可省可不省，但是助动词不能省，为什么答案不是than those burning gasoline or diesel fuel do 呢
1, most ot the times, "do" should not be omitted. but i did see a couple of times where it is omitted. 2, In GMAT, if "do" is not omitted, it tends to be placed in a reverse , eg. ... than do vehicles ...
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发表于 2004-1-8 12:10:00
