[求助]GWD-上面的一个语法题

GWD-TN-4(41)

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

正确答案给的是E，我选的是B。总感觉E中的前两句象是被硬揉在一起的，读着不爽。麻烦NN帮解释下，谢谢。

恩，明白了。谢谢。