Which of the following software programs adds support for geographic objects to PostgreSQL?

PostGIS is an extension for PostgreSQL that provides robust support for geographic objects, enabling the database to handle spatial data. This allows users to store, query, and manipulate geographic information directly within PostgreSQL. PostGIS follows the Simple Features for SQL specification, which makes it possible to perform complex spatial queries and analyses.

The other options serve different purposes in the realm of GIS. ArcGIS is a comprehensive GIS software suite developed by Esri that includes tools for spatial analysis, cartography, and data management but does not natively extend PostgreSQL. QGIS is an open-source desktop GIS application that provides tools for working with spatial data but does not add support to the database itself. Google Earth is primarily a visualization tool that allows users to explore geographic data in a 3D geospatial context. While all these programs are valuable in GIS, only PostGIS directly enhances PostgreSQL with geographic functionality.