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 wide­spread, Algonquian-speaking culture

1.重复  （一级排除 C, D, E ）
people redundantly describes the residents rather than the larger group to which the residents belonged. 

2. 时态：( 一级排除 B, D )
过去完成时没有明确标志

3. 修饰(逻辑主语不一致)：(二级排除C,D,E )
culture that was Algonquian-speaking / Algonquian-speaking culture 修饰不正确

4. 代词：which 不能用来指代人…

5. 简洁：定语从句 that be /who be /which be能省就省。