17. 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 wide-spread, Algonquian-speaking culture

why Native American burial sites dating back ?而不是dated back？

我觉得是因为date back 是个ongoing的动作或说是状态

如果用了dated back 就表示曾经有人把它date back过了

不过我觉得这里应该是无所谓的

如果用dated back，那前面还要加上that