Necessary, because if this isn’t true — if the number of news stories that a person is exposed to is the source of confusion — then that undermines the author’s theory that the reason for confusion must be the poor organization of stories. Notice that the author’s premise concerning information density only related to the density of info in a typical story; this overlooks the potential impact of being exposed to many stories.

Not necessary, because the argument concerns the cause of confusion. One can still be confused by the info in a story, even if it’s possible to understand the info.

Not necessary, because the author believes poor organization is the cause of confusion. So although the author thinks better organization would help someone be less confused, that doesn’t imply the author must think that having more news stories would help someone be less confused.

We know that most people can cope with more density than that found in a typical news story. This doesn’t imply the author thinks most people can cope with a “very high” info density. Maybe the info density of a news story is low, and people can cope with just slightly more.

Not necessary, because the author’s theory is that poor organization is what causes confusion. Poor organization is different from the amount of information.