Native American burial sites dating back 5,000 years indicate that the residents of Maine at that time were part of a widespread culture of Algonquian-speaking people.

(A) were part of a widespread culture of Algonquian-speaking people
(B) had been part of a widespread culture of people who were Algonquian-speaking
(C) were people who were part of a widespread culture that was Algonquian-speaking
(D) had been people who were part of a widespread culture that was Algonquian-speaking
(E) were a people which had been part of a widespread, Algonquian-speaking culture

Please provide OA. To me it looks, A.

Thanks
Mankey