Which of the following basemaps is typically not available through ArcGIS Online?

The reason Land Cover is typically not available as a standard basemap through ArcGIS Online is due to limitations in the types of datasets that are offered as basemaps. ArcGIS Online primarily focuses on providing basemaps that serve general navigation and analysis needs, such as Satellite Imagery, Streets, and Topographic Maps.

Satellite Imagery provides a visual representation of the Earth's surface, which is useful for various applications such as environmental monitoring and urban planning. Streets offer detailed information for navigation, while Topographic Maps give insights into terrain and elevation. On the other hand, Land Cover datasets can be more specialized and may not be as widely used in broad applications compared to the more commonly utilized basemaps.

In summary, while Land Cover data is valuable for specific analyses, it does not fit the standard categories typically found in the basemap offerings on ArcGIS Online, which are designed for wide applicability and everyday use.