89. Dirt roads may evoke the bucolic simplicity of another century, but financially strained townships point out that dirt roads cost twice as much as maintaining paved roads. A.dirt roads cost twice as much as maintaing paved roads
B.dirt roads cost twice as much to maintain as paved roads do C.maintaining dirt roads costs twice as much as paved roads do
D.maintaining dirt roads costs twice as much as it does for paved roads
E.to maintain dirt roads costs twice as much as for paved roads
答案是B
我知道比较的对象是dirt roads和paved roads ,但是我不理解B中的to maintain是什么成分?我选的是C,是不是如果最后没有do,C就是正确的?
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