What map element should be used to identify a province within the entire country on a map?

Using an extent rectangle is essential for highlighting a specific area, such as a province within a country, on a map. This tool visually communicates the relationship between the larger context of the entire country and the specific province being emphasized. By displaying the extent of the province within the overall map of the country, it helps viewers quickly identify the location and spatial context of the province.

This feature is particularly useful when a map contains a lot of detailed information, and there is a need to focus the viewer's attention on a particular area without losing sight of where it fits within the larger geographical scope.

The other options serve different functions: Data Driven Pages allow for the creation of a series of map pages based on a single layout, reference scales assist in maintaining accuracy in size representation on a map, and new graphics layers are utilized for additional drawing or annotation but do not inherently provide the needed context for identifying a specific province within a whole country.