Respuesta :
The correct option is frontier. Unexplored territory is represented as a frontier.
If someone refers to something as "the frontier," whether it be a distant region of land or a brand-new area of study, you are encouraged to investigate it. There are many different definitions for the word frontier. It was defined as "that section of a country which fronts or faces another country or an unsettled region;...extreme part of a country" in Webster's International Dictionary in 1890. According to statistics from the 19th century, it was defined as a region with no fewer than two but no more than six European residents per square mile (fewer than one to just over two Europeans per square kilometre). Areas having lower population densities were classified as "unsettled" by the United States Census Bureau.then for each decade on a set of maps, marked the frontier line. As a result, explorers, missionaries, and trappers were no longer the only people allowed in frontier regions, but established homesteads remained uncommon and dispersed.
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