Which ArcGIS Server License includes the ability to use spatial analyst tools?

The ArcGIS Server License that includes access to spatial analyst tools is the Advanced license. The Advanced level provides comprehensive functionality and is designed for users who need to perform complex spatial analyses, including the full suite of Spatial Analyst tools, which allow for advanced raster-based spatial analysis and modeling.

This capability is crucial for users who require in-depth spatial analysis for tasks such as terrain modeling, hydrologic modeling, and image processing. The Advanced license supports extensive analytical capabilities that are not available in the Basic or Standard licenses, which have more limited analytical functions focused on basic GIS tasks and general mapping capabilities.

Thus, the Advanced license uniquely provides tools and features required for comprehensive spatial analysis, making it the correct answer in this context.