A major reason for the formation of groups like the National Congress of American Indians was

A major reason for the formation of groups like the National Congress of American Indians was to show the Whites that lived East of them that they were not the "savages" that they were as depicted by the newspapers, and that they can adapt and become like the whites. On top of that, it was to give them a structural government to rely on in case the Americans wanted to deport them west. Of course, this did not work, as most, if not all, Native American tribes were deported west.

the inadequacy of efforts to improve the lives of American Indians

Explanation:

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when studying cause and effect, historians usually group the causes into different categories. for example, cultural causes reflect how a society’s literature and art convey the way the society saw itself in relation to the rest of the world. another resource that historians use to understand society is pop culture, which tells them the trends and ideas that are preferred by the common people. when studying cause and effect, it’s important to remember multiple causation, or the idea that an effect could have several causes and vice versa.  

the correct option is “cultural causes” since art and literature are related to the culture of a place. culture is determined by literature, art, music.

the correct option is “pop culture” since it reflects the likes and ideas of common people whereas the rest of the options do not focus on common people.  

the correct option is “multiple causation” since it refers to the idea that events are caused by multiple reasons, not just a single one.