What type of map would be used to show population density across a region?

To effectively show population density across a region, a thematic map is the most appropriate choice. Thematic maps are designed to convey specific themes or topics through spatial representation. In this case, a thematic map would display variations in population density by using color gradations, shading, or symbols across different areas, allowing viewers to quickly understand demographic patterns and distributions.

Reference maps, which focus on providing a general overview of geographic features and locations without emphasizing particular themes, would not effectively communicate the specific information about population density. Similarly, topographic maps, which illustrate terrain relief and landforms, are not suited for representing population density straightforwardly. Road maps, while useful for navigation by indicating routes and roadways, lack the capability to illustrate demographic data, making them an unsuitable choice for this purpose.

Ultimately, thematic maps excel at depicting specific data trends, making them the clear option for visualizing population density.