请教prep新版一道题。。也是gwd的

夏日飘雪

The greatest road system built in the Americas prior to the arrival of Christopher Columbus was the Incan highway, which, over 2,500 miles long and extending from northern Ecuador through Peru to southern Chile.

A. Columbus was the Incan highway, which, over 2,500 miles long and extending

B. Columbus was the Incan highway, over 2,500 miles in length, and extended

C. Columbus, the Incan highway, which was over 2,500 miles in length and extended

D. Columbus, the Incan highway, being over 2,500 miles in length, was extended

E. Columbus, the Incan highway was over 2,500 miles long, extending

哪位帮我分析下，答案是E，我觉得E的前后关系看不出来啊。。。谢谢！！！

夏日飘雪

如果说the greatest road system是the incan highway的同位语，他们是不是距离太远了。。。我会以为the incan highway是Columbus的同位语。。

而且刚开始看原句的时候，是有一种the greatest road system（这里有个修饰）是。。。的感觉，而不是它做同位语成分啊，况且离主语太远了。。

Luxe

E前面那部分是 独立主格，中间是主句，后面是状语