What shape is slightly flattened to approximate Earth's actual shape?

The correct choice is an ellipsoid, which is a geometric shape that closely approximates the physical shape of the Earth. The Earth is not a perfect sphere; rather, it exhibits a slight flattening at the poles and a slight bulging at the equator due to its rotation. This characteristic can be modeled by an ellipsoid, which is mathematically defined as a surface that is formed by rotating an ellipse around one of its principal axes.

Using an ellipsoidal model allows for more accurate calculations of distances, areas, and other geographical metrics on the Earth's surface than a simple spherical model would provide. Hence, in the context of geospatial data and Geographic Information Systems (GIS), representing Earth as an ellipsoid is crucial for precise mapping and analysis.