首先dating back 5000 years应该使用的是过去时,没有确定的过去完成时标志。看整个从句,可以提炼出the residents...were part of a culture的结构,"of..."修饰culture。
notice that the sentence include a reference in time at that time, so simple past is the correct verb tense. Option C presents two problems First is wordier than A Second I think that you cannot say "a culture that was Algonquian-speaking". Can a culture be Algonquian-speaking? Can a culture speak?
sites should belong to part
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