the book stateson page 20 (instructions):

rather than = preference
instead of = in place of another

the question states:
A new theory proposes that Stoneghenge was built to be a monument to the dead rather than serviing as a giant device that tracked celestial events.

I believe the answer should be E - instead of a giant device which

the book states the answer is B - rather than a giant device that

what is the reasoning why E is wrong? The book explnantion is not clear.

Choice E is incorrect because the word "which" (in this case because it is describing an idea) needs to follow a comma.


- Veritas Help

Can you clarify? Why does Which need a comma, and how would the sentence read?
Would all sentences that have the word "Which" require commas? If not which cases?


Further, please explain why the book instructions do not hold for this sentence. Specifically the rather than/ instead of ??