求助NN语法题

GWD6-Q41:

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 

请问下，我选B，over 2,500 miles in length在题中是否可以作为一种修饰？E是正确答案应该怎样理解？谢谢NN指点

我觉得可以作为修饰成分，如果B改成over 2,500 miles in length and extending，应该就没啥错了吧。。

我不是NN，有NN出来comment一下么

应该选E，其中The greatest road system built in the Americas prior to the arrival of Christopher Columbus是the Incan highway的同位语
B的问题很多,首先前半句表达方式比较awkward,如果反过来说the Incan highway was The greatest road system built in the Americas prior to the arrival of Christopher Columbus 还差不多，其次over 2500 miles in length 不好，应为over 2500 miles long,再次，如果后面作为修饰应写成over 2500 miles long and extending.....

GWD6-Q41:

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 

请问下，我选B，over 2,500 miles in length在题中是否可以作为一种修饰？E是正确答案应该怎样理解？谢谢NN指点

B 项的主要错误在于　“,and extended”  这个and extended 与哪一项并列？与主句谓语 was 并列？　还是像你所说的作为一种修饰？　歧义就此产生。所以不能选。