The least important but most complex detail
An error the author needs to correct for clarity
Something the reader should think, feel, or do
I believe that the answer is "something that the reader should think, feel, or do". I believe this because it makes the most sense for one and two when an author is restating an idea it means it is important and they want the reader to feel that it is important too. The author also might want the reader to have emotions toward the idea depending on what it is. I hope I am not too late to answering this question.
If an idea is restated in a nonfiction article the most likely signal is something the reader should think, feel, or do
Nonfiction writing are literature or writing that are true.
They can written from a true story or an individual biography.
Therefore, If an idea is restated in a nonfiction article the most likely signal is something the reader should think, feel, or do
Learn more on nonfiction below
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The United States could not annex Cuba.