求救：gwd30-Q2答案是不是run-on?

2. GWD30-Q2:

Caribou are wary animals with excellent hearing, so stalking them over the treeless landscape, getting close enough to kill it with nothing but a handheld lance, as Dorset people did, required exceptional hunting skill.

A.      so stalking them over the treeless landscape, getting close enough to kill it

B.       so to stalk them over the treeless landscape and get close enough to kill one

C.      so in order to stalk them over the treeless landscape and get close enough to kill one

D.      and so in order to stalk it over the treeless landscape, getting close enough to kill it

E.       and so stalking them over the treeless landscape and getting close enough in order to kill it

哪位NN给看看，so 可以是连词么？答案B是不是一个run on sentence ? 我怎么记得必须得有 and 啊？and so 看起来更好吧？

thanks alot

明白了，谢谢。