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

B is Correct.

对于(D)  OG说: It has no referent; 为什么呢? 我记得见过几次这种表达啊  比如:"For those other clans, access to water was less limited than it was for the Anasazi."  这句是705页上第98题的解释里的一句话; OG自己都这么用啊

OG说没有指代对象就是没有指代对象

如果IT指代了maintaining dirt roads，如果变成maintaining dirt road就正确了的话，那后面的 paved roads是什么？(maintaining dirt road) does for paved roads太错了，it does(costs)  for paved roads看起来好像IT要和前面保持平行，但cost 这个动作本来是paved roads发出的，现在成了it发出，it是什么又不知道.

不晓得我理解的对不对

偶到是觉得 cost 这个动作不是paved roads发出的 而是 maintaining paved roads 发出的 我的疑问就是 it 能不能仅指代“maintaining”？有点怪哈   因为看我举的那句话：:"For those other clans, access to water was less limited than it was for the Anasazi."  这个IT明显指的就是access