How do choropleth maps use colors? colors are used to represent changes in climate zones. varying colors are used to indicate territorial boundaries and changes. darker colors are used to indicate greater amounts of what is being measured. colors are used to highlight historical trends of the topic being studied.

The correct answer is the third statement. Choropleth  maps are based on statistical data that are shown through different color ranges in which darker colors are used to indicate greater amounts on the data shed and the lightest shade indicates the least amount of what is being measured on data shed. 

A choropleth map is a thematic map in which areas are shaded or patterned in proportion to the measurement of the statistical variable being displayed on the map, such as population density or per-capita income. The following statement is true: Darker colors are used to indicate greater amounts of what is being measured.

i think the answer to your question is: settlement of the interior and economic growth. ( ^_^)／