What is an unstated central idea?

Responses

an idea that has been expressed so often that it does not have to be repeated
an idea that has been expressed so often that it does not have to be repeated

an idea that is either too controversial or too hard to prove
an idea that is either too controversial or too hard to prove

an idea that the reader infers because the author has not expressed it directly
an idea that the reader infers because the author has not expressed it directly

an idea that the author decided not to include in the text because it might be distracting
an idea that the author decided not to include in the text because it might be distracting

an idea that the author decided not to include in the text because it might be distracting