According to the passage, an important focus of research for scholars of Native American oral literature has been A. tracing the influence of European tales on Native American narrative traditions B. reconstructing the form in which Native American tales existed prior to being influenced by European narrative elements C. documenting how Native American oral traditions have influenced one another D. identifying features of Native American narratives that betray European influences E. analyzing the significance of differences that appear in particular Native American narratives after exposure to European influence