To determine the best location for a geothermal electrical generator, we typically consider factors such as proximity to geothermal hotspots, accessibility, and environmental impact. Without seeing the map you are referring to, I can't provide a specific answer.
However, generally, the best location is usually one that is near tectonic activity, such as near tectonic plate boundaries or volcanic areas, where geothermal energy is more readily available.
If you can provide more details about the map or the locations (A, B, C, or D) and their characteristics, I would be happy to help further!