Sentence Correction (SC) | Re: The remarkable similarity of Thule artifacts throughout a vast region

Hello experts,

I think the meaning changes when we say-in parts and one explanation.
It changes from- the reason is partially responsible- to- one of the explanation out of many or some explanations-

1. Right? Or their meaning is different from mine?

Hence I thought D is changing the meaning.
I was keeping original choice’s meaning as the right meaning.

2. Also, when as is used as a reason, doesn’t it require a clause?
The only clause after as
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