Answer:
the frontier had meant that every American generation returned "to primitive conditions on a continually advancing frontier line." Along this frontier -- which he also described as "the meeting point between savagery and civilization"
Explanation:
Hope I helped! if not im sorry.
I think that the answer is D) prosperous, because remember, the Americans won World War 2, and when they won, they brought back with them a period of prosperity and made the United States one of the richest countries in the world.
~Hope I helped!~
