SC PREP2的一个问题

lainemai

Caribouare wary animals with excellent hearing, so stalking them over the treelesslandscape, getting close enough to kill it with nothing but a handheldlance, as Dorset people did, required exceptional hunting skill.

A so stalking them over the treelesslandscape, getting close enough to kill it

B so to stalk them over the treelesslandscape and get close enough to kill one

C so in order to stalk them over the treelesslandscape and get close enough to kill one

D and so in order to stalk it over thetreeless landscape, getting close enough to kill it

E and so stalking them over the treelesslandscape and getting close enough in order to kill it

这道题正确选项是C，我当时选了E，然后看E的解析是这样的：and后半句没有主句；in order to kill不如to kill简洁。
我想知道and后半句没有主句这句话是什么意思，我当初的理解就是stalking......and getting这两个是平行并列的，怎么会涉及到有没有主句的问题？那要是这么看正确答案的and后面不是也一样没有主句了吗？