According to the Geo-scientists, the shape of the earth is described as an "oblate ellipsoid." An oblate ellipsoid is a three-dimensional geometric shape that is similar to a sphere but slightly flattened at the poles and bulging at the equator.

Option 1 states that the shape of the earth is "round." While this is true, it is not specific enough, as many objects can be considered round.

Option 2 states that the shape of the earth is "spherical." This is partially correct, as an oblate ellipsoid can also be described as a sphere. However, it does not provide the additional information about the shape being slightly flattened at the poles.

Option 3 states that the shape of the earth is "close to that of a sphere." This is also partially correct, as an oblate ellipsoid is similar to a sphere, but the word "close" leaves room for ambiguity.

Option 4 correctly identifies the shape of the earth as an "oblate ellipsoid." This option is the best answer because it provides the most accurate and specific description of the shape of the earth as determined by Geo-scientists.