Sentence Correction (SC) | Re: Finally reaching a decision on an issue that has long been politically

I know that A is wrong , but is it wrong because of usage of 'instead of which' or is it because of usage of 'bywhich'

Finally reaching a decision on an issue that has long been politically charged in the Pacific Northwest, politicians decided to postpone by at least five years an ambitious plan to protect wild salmon and other endangered fish, instead of[color=#ff0000]
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