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

 答案选E。有没有那位NN能解释下D错在哪了？网上有人说是being错了，为什么错呢，那正确的应该是什么呢？