GMAT Sentence Correction (SC) | Re: In 1985, fewer than 1 million wild boars inhabited approxima

Hi sayantanc2k and experts,
Humbly request you to weight in this question.
To me "who" should refer back to Rosen,not research group.
Additionally,can I eliminate option E since appositive modifier can't be parallel with relative pronoun(who)?

Thanks for your help

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