A futuristic novel tells the story of the United States after a nuclear disaster. People live separately in underground bunkers, where they
cannot contact those in different bunkers. Civilization survives for
many generations, but each isolated group develops differently. While
some people are still able to find a degree of happiness, others suffer
under cruel dictators or live in terrible conditions. Without any
awareness of the other survivors, each group has to make do without
important goods and abilities, and those who suffer have no idea that
life could be better.
Which is the best explanation of how the setting helps to reveal the theme?

PLZZ ASA